diff --git a/react/features/base/conference/reducer.ts b/react/features/base/conference/reducer.ts
index a96885c8b..3079949e2 100644
--- a/react/features/base/conference/reducer.ts
+++ b/react/features/base/conference/reducer.ts
@@ -50,6 +50,7 @@ export interface IJitsiConference {
     getBreakoutRooms: Function;
     getLocalParticipantProperty: Function;
     getLocalTracks: Function;
+    getParticipantById: Function;
     grantOwner: Function;
     isAVModerationSupported: Function;
     isCallstatsEnabled: Function;
@@ -74,6 +75,8 @@ export interface IJitsiConference {
     setDesktopSharingFrameRate: Function;
     setDisplayName: Function;
     setLocalParticipantProperty: Function;
+    setReceiverConstraints: Function;
+    setSenderVideoConstraint: Function;
     setSubject: Function;
 }
 
diff --git a/react/features/base/config/configType.ts b/react/features/base/config/configType.ts
index 419d2354f..8a8a406bd 100644
--- a/react/features/base/config/configType.ts
+++ b/react/features/base/config/configType.ts
@@ -433,7 +433,7 @@ export interface IConfig {
         disableSearch?: boolean;
         disabled?: boolean;
         order?: Array<'role' | 'name' | 'hasLeft'>;
-     };
+    };
     speakerStatsOrder?: Array<'role' | 'name' | 'hasLeft'>;
     startAudioMuted?: number;
     startAudioOnly?: boolean;
@@ -492,6 +492,7 @@ export interface IConfig {
         minHeightForQualityLvl?: {
             [key: number]: string;
         };
+        persist?: boolean;
         preferredCodec?: string;
         resizeDesktopForPresenter?: boolean;
     };
diff --git a/react/features/base/tracks/functions.ts b/react/features/base/tracks/functions.ts
index ba054067a..54083ab37 100644
--- a/react/features/base/tracks/functions.ts
+++ b/react/features/base/tracks/functions.ts
@@ -496,7 +496,7 @@ export function getVirtualScreenshareParticipantTrack(tracks: ITrack[], virtualS
  * @param {string[]} screenShareParticipantIds - Participant ID.
  * @returns {(string[])}
  */
-export function getRemoteScreenSharesSourceNames(state: IReduxState, screenShareParticipantIds = []) {
+export function getRemoteScreenSharesSourceNames(state: IReduxState, screenShareParticipantIds: string[] = []) {
     const tracks = state['features/base/tracks'];
 
     return getMultipleVideoSupportFeatureFlag(state)
diff --git a/react/features/follow-me/actions.js b/react/features/follow-me/actions.ts
similarity index 84%
rename from react/features/follow-me/actions.js
rename to react/features/follow-me/actions.ts
index ac64cbdb8..c6acbef46 100644
--- a/react/features/follow-me/actions.js
+++ b/react/features/follow-me/actions.ts
@@ -1,5 +1,3 @@
-// @flow
-
 import {
     SET_FOLLOW_ME_MODERATOR,
     SET_FOLLOW_ME_STATE
@@ -14,7 +12,7 @@ import {
  *     id, string
  * }}
  */
-export function setFollowMeModerator(id: ?string) {
+export function setFollowMeModerator(id?: string) {
     return {
         type: SET_FOLLOW_ME_MODERATOR,
         id
@@ -30,7 +28,7 @@ export function setFollowMeModerator(id: ?string) {
  *     state: Object
  * }}
  */
-export function setFollowMeState(state: ?Object) {
+export function setFollowMeState(state?: Object) {
     return {
         type: SET_FOLLOW_ME_STATE,
         state
diff --git a/react/features/follow-me/functions.js b/react/features/follow-me/functions.ts
similarity index 69%
rename from react/features/follow-me/functions.js
rename to react/features/follow-me/functions.ts
index ca23a87e3..25c22f871 100644
--- a/react/features/follow-me/functions.js
+++ b/react/features/follow-me/functions.ts
@@ -1,6 +1,5 @@
-// @flow
-
-import { toState } from '../base/redux';
+import { IStateful } from '../base/app/types';
+import { toState } from '../base/redux/functions';
 
 /**
  * Returns true if follow me is active and false otherwise.
@@ -9,7 +8,7 @@ import { toState } from '../base/redux';
  * to the Redux state.
  * @returns {boolean} - True if follow me is active and false otherwise.
  */
-export function isFollowMeActive(stateful: Object | Function) {
+export function isFollowMeActive(stateful: IStateful) {
     const state = toState(stateful);
 
     return Boolean(state['features/follow-me'].moderator);
diff --git a/react/features/follow-me/logger.js b/react/features/follow-me/logger.ts
similarity index 91%
rename from react/features/follow-me/logger.js
rename to react/features/follow-me/logger.ts
index 0853fd3de..5ead2a375 100644
--- a/react/features/follow-me/logger.js
+++ b/react/features/follow-me/logger.ts
@@ -1,5 +1,3 @@
-// @flow
-
 import { getLogger } from '../base/logging/functions';
 
 export default getLogger('features/follow-me');
diff --git a/react/features/follow-me/middleware.js b/react/features/follow-me/middleware.ts
similarity index 85%
rename from react/features/follow-me/middleware.js
rename to react/features/follow-me/middleware.ts
index 778740cb6..44294d2bf 100644
--- a/react/features/follow-me/middleware.js
+++ b/react/features/follow-me/middleware.ts
@@ -1,19 +1,16 @@
-// @flow
-
 import _ from 'lodash';
 
+import { IStore } from '../app/types';
 import { CONFERENCE_JOIN_IN_PROGRESS } from '../base/conference/actionTypes';
-import {
-    PARTICIPANT_LEFT,
-    getParticipantById,
-    getPinnedParticipant,
-    pinParticipant
-} from '../base/participants';
-import { MiddlewareRegistry } from '../base/redux';
-import { updateSettings } from '../base/settings';
-import { setFilmstripVisible } from '../filmstrip';
-import { addStageParticipant } from '../filmstrip/actions.web';
-import { setTileView } from '../video-layout';
+import { PARTICIPANT_LEFT } from '../base/participants/actionTypes';
+import { pinParticipant } from '../base/participants/actions';
+import { getParticipantById, getPinnedParticipant } from '../base/participants/functions';
+import MiddlewareRegistry from '../base/redux/MiddlewareRegistry';
+import { updateSettings } from '../base/settings/actions';
+// eslint-disable-next-line lines-around-comment
+// @ts-ignore
+import { addStageParticipant, setFilmstripVisible } from '../filmstrip/actions';
+import { setTileView } from '../video-layout/actions.any';
 
 import {
     setFollowMeModerator,
@@ -25,8 +22,6 @@ import logger from './logger';
 
 import './subscriber';
 
-declare var APP: Object;
-
 /**
  * The timeout after which a follow-me command that has been received will be
  * ignored if not consumed.
@@ -43,7 +38,7 @@ const _FOLLOW_ME_RECEIVED_TIMEOUT = 30;
  *
  * @type {TimeoutID}
  */
-let nextOnStageTimeout;
+let nextOnStageTimeout: number;
 
 /**
  * A count of how many seconds the nextOnStageTimeout has ticked while waiting
@@ -66,7 +61,7 @@ MiddlewareRegistry.register(store => next => action => {
         const { conference } = action;
 
         conference.addCommandListener(
-            FOLLOW_ME_COMMAND, ({ attributes }, id) => {
+            FOLLOW_ME_COMMAND, ({ attributes }: any, id: string) => {
                 _onFollowMeCommand(attributes, id, store);
             });
         break;
@@ -94,7 +89,7 @@ MiddlewareRegistry.register(store => next => action => {
  * @private
  * @returns {void}
  */
-function _onFollowMeCommand(attributes = {}, id, store) {
+function _onFollowMeCommand(attributes: any = {}, id: string, store: IStore) {
     const state = store.getState();
 
     // We require to know who issued the command because (1) only a
@@ -124,7 +119,7 @@ function _onFollowMeCommand(attributes = {}, id, store) {
         const { conference } = state['features/base/conference'];
 
         // As this participant is not stored in redux store we do the checks on the JitsiParticipant from lib-jitsi-meet
-        const participant = conference.getParticipantById(id);
+        const participant = conference?.getParticipantById(id);
 
         if (!iAmRecorder || !participant || participant.getRole() !== 'moderator'
             || !participant.isHiddenFromRecorder()) {
@@ -187,7 +182,8 @@ function _onFollowMeCommand(attributes = {}, id, store) {
         const stageParticipants = JSON.parse(attributes.pinnedStageParticipants);
 
         if (!_.isEqual(stageParticipants, oldState.pinnedStageParticipants)) {
-            stageParticipants.forEach(p => store.dispatch(addStageParticipant(p.participantId, true)));
+            stageParticipants.forEach((p: { participantId: string; }) =>
+                store.dispatch(addStageParticipant(p.participantId, true)));
         }
     }
 
@@ -207,14 +203,14 @@ function _onFollowMeCommand(attributes = {}, id, store) {
  * @private
  * @returns {void}
  */
-function _pinVideoThumbnailById(store, clickId) {
+function _pinVideoThumbnailById(store: IStore, clickId: string) {
     if (getParticipantById(store.getState(), clickId)) {
         clearTimeout(nextOnStageTimeout);
         nextOnStageTimer = 0;
 
         store.dispatch(pinParticipant(clickId));
     } else {
-        nextOnStageTimeout = setTimeout(() => {
+        nextOnStageTimeout = window.setTimeout(() => {
             if (nextOnStageTimer > _FOLLOW_ME_RECEIVED_TIMEOUT) {
                 nextOnStageTimer = 0;
 
diff --git a/react/features/follow-me/subscriber.js b/react/features/follow-me/subscriber.ts
similarity index 91%
rename from react/features/follow-me/subscriber.js
rename to react/features/follow-me/subscriber.ts
index 82a4db8ef..71af651da 100644
--- a/react/features/follow-me/subscriber.js
+++ b/react/features/follow-me/subscriber.ts
@@ -1,11 +1,12 @@
-// @flow
-
-import { getCurrentConference } from '../base/conference';
+import { IReduxState, IStore } from '../app/types';
+import { getCurrentConference } from '../base/conference/functions';
 import {
     getPinnedParticipant,
     isLocalParticipantModerator
-} from '../base/participants';
-import { StateListenerRegistry } from '../base/redux';
+} from '../base/participants/functions';
+import StateListenerRegistry from '../base/redux/StateListenerRegistry';
+// eslint-disable-next-line lines-around-comment
+// @ts-ignore
 import { getPinnedActiveParticipants, isStageFilmstripEnabled } from '../filmstrip/functions.web';
 import { shouldDisplayTileView } from '../video-layout/functions';
 
@@ -84,14 +85,14 @@ StateListenerRegistry.register(
  * @param {Object} state - The redux state.
  * @returns {Object}
  */
-function _getFollowMeState(state) {
+function _getFollowMeState(state: IReduxState) {
     const pinnedParticipant = getPinnedParticipant(state);
     const stageFilmstrip = isStageFilmstripEnabled(state);
 
     return {
         filmstripVisible: state['features/filmstrip'].visible,
         maxStageParticipants: stageFilmstrip ? state['features/base/settings'].maxStageParticipants : undefined,
-        nextOnStage: stageFilmstrip ? undefined : pinnedParticipant && pinnedParticipant.id,
+        nextOnStage: stageFilmstrip ? undefined : pinnedParticipant?.id,
         pinnedStageParticipants: stageFilmstrip ? JSON.stringify(getPinnedActiveParticipants(state)) : undefined,
         sharedDocumentVisible: state['features/etherpad'].editing,
         tileViewEnabled: shouldDisplayTileView(state)
@@ -107,7 +108,7 @@ function _getFollowMeState(state) {
  * @returns {void}
  */
 function _sendFollowMeCommand(
-        newSelectedValue, store) { // eslint-disable-line no-unused-vars
+        newSelectedValue: any, store: IStore) {
     const state = store.getState();
     const conference = getCurrentConference(state);
 
diff --git a/react/features/shared-video/functions.js b/react/features/shared-video/functions.ts
similarity index 89%
rename from react/features/shared-video/functions.js
rename to react/features/shared-video/functions.ts
index efbc7c97d..a41c1ffcc 100644
--- a/react/features/shared-video/functions.js
+++ b/react/features/shared-video/functions.ts
@@ -1,6 +1,5 @@
-// @flow
-
-import { getFakeParticipants } from '../base/participants';
+import { IStateful } from '../base/app/types';
+import { getFakeParticipants } from '../base/participants/functions';
 
 import { VIDEO_PLAYER_PARTICIPANT_NAME, YOUTUBE_PLAYER_PARTICIPANT_NAME } from './constants';
 
@@ -40,10 +39,10 @@ export function isSharingStatus(status: string) {
  * @param {Object | Function} stateful - The Redux state or a function that gets resolved to the Redux state.
  * @returns {boolean}
  */
-export function isVideoPlaying(stateful: Object | Function): boolean {
+export function isVideoPlaying(stateful: IStateful): boolean {
     let videoPlaying = false;
 
-    // eslint-disable-next-line no-unused-vars
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
     for (const [ id, p ] of getFakeParticipants(stateful)) {
         if (p.name === VIDEO_PLAYER_PARTICIPANT_NAME || p.name === YOUTUBE_PLAYER_PARTICIPANT_NAME) {
             videoPlaying = true;
diff --git a/react/features/video-layout/actions.any.js b/react/features/video-layout/actions.any.ts
similarity index 92%
rename from react/features/video-layout/actions.any.js
rename to react/features/video-layout/actions.any.ts
index ef645fe27..5e5201085 100644
--- a/react/features/video-layout/actions.any.js
+++ b/react/features/video-layout/actions.any.ts
@@ -1,6 +1,4 @@
-// @flow
-
-import type { Dispatch } from 'redux';
+import { IStore } from '../app/types';
 
 import {
     SCREEN_SHARE_REMOTE_PARTICIPANTS_UPDATED,
@@ -54,7 +52,7 @@ export function virtualScreenshareParticipantsUpdated(participantIds: Array<stri
  *     enabled: ?boolean
  * }}
  */
-export function setTileView(enabled: ?boolean) {
+export function setTileView(enabled?: boolean) {
     return {
         type: SET_TILE_VIEW,
         enabled
@@ -68,7 +66,7 @@ export function setTileView(enabled: ?boolean) {
  * @returns {Function}
  */
 export function toggleTileView() {
-    return (dispatch: Dispatch<any>, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         const tileViewActive = shouldDisplayTileView(getState());
 
         dispatch(setTileView(!tileViewActive));
diff --git a/react/features/video-layout/actions.native.js b/react/features/video-layout/actions.native.ts
similarity index 100%
rename from react/features/video-layout/actions.native.js
rename to react/features/video-layout/actions.native.ts
diff --git a/react/features/video-layout/actions.web.js b/react/features/video-layout/actions.web.ts
similarity index 100%
rename from react/features/video-layout/actions.web.js
rename to react/features/video-layout/actions.web.ts
diff --git a/react/features/video-layout/functions.any.js b/react/features/video-layout/functions.any.ts
similarity index 87%
rename from react/features/video-layout/functions.any.js
rename to react/features/video-layout/functions.any.ts
index 5ae950af9..14ece6141 100644
--- a/react/features/video-layout/functions.any.js
+++ b/react/features/video-layout/functions.any.ts
@@ -1,13 +1,11 @@
-// @flow
-import type { Dispatch } from 'redux';
-
-import { TILE_VIEW_ENABLED, getFeatureFlag } from '../base/flags';
-import {
-    getParticipantCount,
-    getPinnedParticipant,
-    pinParticipant
-} from '../base/participants';
+import { IReduxState, IStore } from '../app/types';
+import { TILE_VIEW_ENABLED } from '../base/flags/constants';
+import { getFeatureFlag } from '../base/flags/functions';
+import { pinParticipant } from '../base/participants/actions';
+import { getParticipantCount, getPinnedParticipant } from '../base/participants/functions';
 import { FakeParticipant } from '../base/participants/types';
+// eslint-disable-next-line lines-around-comment
+// @ts-ignore
 import { isStageFilmstripAvailable } from '../filmstrip/functions';
 import { isVideoPlaying } from '../shared-video/functions';
 import { VIDEO_QUALITY_LEVELS } from '../video-quality/constants';
@@ -16,8 +14,6 @@ import { getMinHeightForQualityLvlMap } from '../video-quality/selector';
 
 import { LAYOUTS } from './constants';
 
-declare var interfaceConfig: Object;
-
 /**
  * A selector for retrieving the current automatic pinning setting.
  *
@@ -40,7 +36,7 @@ export function getAutoPinSetting() {
  * @param {Object} state - The redux state.
  * @returns {string}
  */
-export function getCurrentLayout(state: Object) {
+export function getCurrentLayout(state: IReduxState) {
     if (navigator.product === 'ReactNative') {
         // FIXME: what should this return?
         return undefined;
@@ -65,8 +61,8 @@ export function getCurrentLayout(state: Object) {
  * @param {Object} state - The redux state.
  * @returns {boolean} True if tile view should be displayed.
  */
-export function shouldDisplayTileView(state: Object = {}) {
-    const { tileViewEnabled } = state['features/video-layout'];
+export function shouldDisplayTileView(state: IReduxState) {
+    const { tileViewEnabled } = state['features/video-layout'] ?? {};
 
     if (tileViewEnabled !== undefined) {
         // If the user explicitly requested a view mode, we
@@ -119,7 +115,7 @@ export function shouldDisplayTileView(state: Object = {}) {
  * @returns {void}
  */
 export function updateAutoPinnedParticipant(
-        screenShares: Array<string>, { dispatch, getState }: { dispatch: Dispatch<any>, getState: Function }) {
+        screenShares: Array<string>, { dispatch, getState }: IStore) {
     const state = getState();
     const remoteScreenShares = state['features/video-layout'].remoteScreenShares;
     const pinned = getPinnedParticipant(getState);
@@ -155,7 +151,7 @@ export function updateAutoPinnedParticipant(
  * @param {Object} state - The redux state.
  * @returns {boolean}
  */
-export function isLayoutTileView(state: Object) {
+export function isLayoutTileView(state: IReduxState) {
     return getCurrentLayout(state) === LAYOUTS.TILE_VIEW;
 }
 
@@ -189,7 +185,7 @@ function getVideoQualityForHeight(height: number) {
  * @param {Object} state - Redux state.
  * @returns {number}
  */
-export function getVideoQualityForResizableFilmstripThumbnails(height, state) {
+export function getVideoQualityForResizableFilmstripThumbnails(height: number, state: IReduxState) {
     if (!height) {
         return VIDEO_QUALITY_LEVELS.LOW;
     }
@@ -204,7 +200,7 @@ export function getVideoQualityForResizableFilmstripThumbnails(height, state) {
  * @param {Object} state - Redux state.
  * @returns {number}
  */
-export function getVideoQualityForScreenSharingFilmstrip(height, state) {
+export function getVideoQualityForScreenSharingFilmstrip(height: number, state: IReduxState) {
     if (!height) {
         return VIDEO_QUALITY_LEVELS.LOW;
     }
@@ -218,7 +214,7 @@ export function getVideoQualityForScreenSharingFilmstrip(height, state) {
  * @param {number} largeVideoHeight - The height of the large video.
  * @returns {number} - The video quality for the large video.
  */
-export function getVideoQualityForLargeVideo(largeVideoHeight) {
+export function getVideoQualityForLargeVideo(largeVideoHeight: number) {
     return getVideoQualityForHeight(largeVideoHeight);
 }
 
@@ -229,7 +225,7 @@ export function getVideoQualityForLargeVideo(largeVideoHeight) {
  * @param {Object} state - Redux state.
  * @returns {number}
  */
-export function getVideoQualityForStageThumbnails(height, state) {
+export function getVideoQualityForStageThumbnails(height: number, state: IReduxState) {
     if (!height) {
         return VIDEO_QUALITY_LEVELS.LOW;
     }
diff --git a/react/features/video-layout/functions.native.js b/react/features/video-layout/functions.native.ts
similarity index 100%
rename from react/features/video-layout/functions.native.js
rename to react/features/video-layout/functions.native.ts
diff --git a/react/features/video-layout/functions.web.js b/react/features/video-layout/functions.web.ts
similarity index 89%
rename from react/features/video-layout/functions.web.js
rename to react/features/video-layout/functions.web.ts
index 349814d07..9703466e6 100644
--- a/react/features/video-layout/functions.web.js
+++ b/react/features/video-layout/functions.web.ts
@@ -1,3 +1,4 @@
+import { IReduxState } from '../app/types';
 import {
     ABSOLUTE_MAX_COLUMNS,
     DEFAULT_MAX_COLUMNS,
@@ -7,12 +8,12 @@ import {
     getNumberOfPartipantsForTileView,
     getThumbnailMinHeight,
     getTileDefaultAspectRatio
-} from '../filmstrip/functions';
+
+    // @ts-ignore
+} from '../filmstrip/functions.web';
 
 export * from './functions.any';
 
-declare var interfaceConfig: Object;
-
 /**
  * Returns how many columns should be displayed in tile view. The number
  * returned will be between 1 and 7, inclusive.
@@ -24,7 +25,8 @@ declare var interfaceConfig: Object;
  * @param {boolean} options.disableTileEnlargement - Custom value to be used instead of config.disableTileEnlargement.
  * @returns {number}
  */
-export function getMaxColumnCount(state, options = {}) {
+export function getMaxColumnCount(state: IReduxState, options: {
+    disableResponsiveTiles?: boolean; disableTileEnlargement?: boolean; width?: number; } = {}) {
     if (typeof interfaceConfig === 'undefined') {
         return DEFAULT_MAX_COLUMNS;
     }
@@ -69,7 +71,7 @@ export function getMaxColumnCount(state, options = {}) {
  * @returns {Object} An object is return with the desired number of columns,
  * rows, and visible rows (the rest should overflow) for the tile view layout.
  */
-export function getNotResponsiveTileViewGridDimensions(state: Object, stageFilmstrip: boolean = false) {
+export function getNotResponsiveTileViewGridDimensions(state: IReduxState, stageFilmstrip = false) {
     const maxColumns = getMaxColumnCount(state);
     const { activeParticipants } = state['features/filmstrip'];
     const numberOfParticipants = stageFilmstrip ? activeParticipants.length : getNumberOfPartipantsForTileView(state);
diff --git a/react/features/video-layout/logger.js b/react/features/video-layout/logger.ts
similarity index 91%
rename from react/features/video-layout/logger.js
rename to react/features/video-layout/logger.ts
index d03405939..d2f3a8dc4 100644
--- a/react/features/video-layout/logger.js
+++ b/react/features/video-layout/logger.ts
@@ -1,5 +1,3 @@
-// @flow
-
 import { getLogger } from '../base/logging/functions';
 
 export default getLogger('features/video-layout');
diff --git a/react/features/video-layout/middleware.any.js b/react/features/video-layout/middleware.any.ts
similarity index 80%
rename from react/features/video-layout/middleware.any.js
rename to react/features/video-layout/middleware.any.ts
index 416049bbb..288265a92 100644
--- a/react/features/video-layout/middleware.any.js
+++ b/react/features/video-layout/middleware.any.ts
@@ -1,19 +1,17 @@
-// @flow
-
-import { getCurrentConference } from '../base/conference';
-import { VIDEO_TYPE } from '../base/media';
-import {
-    PARTICIPANT_LEFT,
-    PIN_PARTICIPANT,
-    getParticipantById,
-    getPinnedParticipant,
-    pinParticipant
-} from '../base/participants';
-import { MiddlewareRegistry, StateListenerRegistry } from '../base/redux';
-import { TRACK_REMOVED } from '../base/tracks';
-import { SET_DOCUMENT_EDITING_STATUS } from '../etherpad';
+import { IStore } from '../app/types';
+import { getCurrentConference } from '../base/conference/functions';
+import { VIDEO_TYPE } from '../base/media/constants';
+import { PARTICIPANT_LEFT, PIN_PARTICIPANT } from '../base/participants/actionTypes';
+import { pinParticipant } from '../base/participants/actions';
+import { getParticipantById, getPinnedParticipant } from '../base/participants/functions';
+import MiddlewareRegistry from '../base/redux/MiddlewareRegistry';
+import StateListenerRegistry from '../base/redux/StateListenerRegistry';
+import { TRACK_REMOVED } from '../base/tracks/actionTypes';
+import { SET_DOCUMENT_EDITING_STATUS } from '../etherpad/actionTypes';
+// eslint-disable-next-line lines-around-comment
+// @ts-ignore
 import { isStageFilmstripEnabled } from '../filmstrip/functions';
-import { isFollowMeActive } from '../follow-me';
+import { isFollowMeActive } from '../follow-me/functions';
 
 import { SET_TILE_VIEW } from './actionTypes';
 import { setRemoteParticipantsWithScreenShare, setTileView } from './actions';
@@ -21,7 +19,7 @@ import { getAutoPinSetting, updateAutoPinnedParticipant } from './functions';
 
 import './subscriber';
 
-let previousTileViewEnabled;
+let previousTileViewEnabled: boolean | undefined;
 
 /**
  * Middleware which intercepts actions and updates tile view related state.
@@ -88,7 +86,7 @@ MiddlewareRegistry.register(store => next => action => {
     case TRACK_REMOVED: {
         const { jitsiTrack } = action.track;
 
-        if (jitsiTrack && jitsiTrack.isVideoTrack() && jitsiTrack.getVideoType() === VIDEO_TYPE.DESKTOP) {
+        if (jitsiTrack?.isVideoTrack() && jitsiTrack?.getVideoType() === VIDEO_TYPE.DESKTOP) {
             const participantId = jitsiTrack.getParticipantId();
             const oldScreenShares = store.getState()['features/video-layout'].remoteScreenShares || [];
             const newScreenShares = oldScreenShares.filter(id => id !== participantId);
@@ -134,7 +132,7 @@ StateListenerRegistry.register(
  * @param {Object} store - The Redux Store.
  * @returns {void}
  */
-function _restoreTileViewState({ dispatch, getState }) {
+function _restoreTileViewState({ dispatch, getState }: IStore) {
     const { tileViewEnabled } = getState()['features/video-layout'];
 
     if (tileViewEnabled === undefined && previousTileViewEnabled !== undefined) {
@@ -150,7 +148,7 @@ function _restoreTileViewState({ dispatch, getState }) {
  * @param {Object} store - The Redux Store.
  * @returns {void}
  */
-function _storeTileViewStateAndClear({ dispatch, getState }) {
+function _storeTileViewStateAndClear({ dispatch, getState }: IStore) {
     const { tileViewEnabled } = getState()['features/video-layout'];
 
     if (tileViewEnabled !== undefined) {
diff --git a/react/features/video-layout/middleware.native.js b/react/features/video-layout/middleware.native.ts
similarity index 73%
rename from react/features/video-layout/middleware.native.js
rename to react/features/video-layout/middleware.native.ts
index ba2760493..8329a8020 100644
--- a/react/features/video-layout/middleware.native.js
+++ b/react/features/video-layout/middleware.native.ts
@@ -1,6 +1,9 @@
-import { MEDIA_TYPE, VIDEO_MUTISM_AUTHORITY, setVideoMuted } from '../base/media';
-import { MiddlewareRegistry } from '../base/redux';
-import { CLIENT_RESIZED } from '../base/responsive-ui';
+import { setVideoMuted } from '../base/media/actions';
+import { MEDIA_TYPE, VIDEO_MUTISM_AUTHORITY } from '../base/media/constants';
+import MiddlewareRegistry from '../base/redux/MiddlewareRegistry';
+import { CLIENT_RESIZED } from '../base/responsive-ui/actionTypes';
+// eslint-disable-next-line lines-around-comment
+// @ts-ignore
 import { setLargeVideoDimensions } from '../large-video/actions.any';
 
 import { SET_CAR_MODE } from './actionTypes';
diff --git a/react/features/video-layout/middleware.web.js b/react/features/video-layout/middleware.web.ts
similarity index 85%
rename from react/features/video-layout/middleware.web.js
rename to react/features/video-layout/middleware.web.ts
index 7862ee3c8..a7919bbf8 100644
--- a/react/features/video-layout/middleware.web.js
+++ b/react/features/video-layout/middleware.web.ts
@@ -1,15 +1,11 @@
-// @flow
-
+// @ts-expect-error
 import VideoLayout from '../../../modules/UI/videolayout/VideoLayout.js';
-import { CONFERENCE_WILL_LEAVE } from '../base/conference';
-import { MEDIA_TYPE } from '../base/media';
-import {
-    PARTICIPANT_JOINED,
-    PARTICIPANT_UPDATED,
-    getLocalParticipant
-} from '../base/participants';
-import { MiddlewareRegistry } from '../base/redux';
-import { TRACK_ADDED, TRACK_REMOVED, TRACK_STOPPED } from '../base/tracks';
+import { CONFERENCE_WILL_LEAVE } from '../base/conference/actionTypes';
+import { MEDIA_TYPE } from '../base/media/constants';
+import { PARTICIPANT_JOINED, PARTICIPANT_UPDATED } from '../base/participants/actionTypes';
+import { getLocalParticipant } from '../base/participants/functions';
+import MiddlewareRegistry from '../base/redux/MiddlewareRegistry';
+import { TRACK_ADDED, TRACK_REMOVED, TRACK_STOPPED } from '../base/tracks/actionTypes';
 import { PARTICIPANTS_PANE_CLOSE, PARTICIPANTS_PANE_OPEN } from '../participants-pane/actionTypes';
 
 import './middleware.any';
diff --git a/react/features/video-layout/subscriber.js b/react/features/video-layout/subscriber.ts
similarity index 87%
rename from react/features/video-layout/subscriber.js
rename to react/features/video-layout/subscriber.ts
index 063824ab5..c52cc9813 100644
--- a/react/features/video-layout/subscriber.js
+++ b/react/features/video-layout/subscriber.ts
@@ -1,13 +1,13 @@
-// @flow
-
 import debounce from 'lodash/debounce';
 
-import { getMultipleVideoSupportFeatureFlag } from '../base/config';
-import { StateListenerRegistry, equals } from '../base/redux';
-import { isFollowMeActive } from '../follow-me';
+import { getMultipleVideoSupportFeatureFlag } from '../base/config/functions';
+import StateListenerRegistry from '../base/redux/StateListenerRegistry';
+import { equals } from '../base/redux/functions';
+import { ITrack } from '../base/tracks/reducer';
+import { isFollowMeActive } from '../follow-me/functions';
 
-import { setRemoteParticipantsWithScreenShare, virtualScreenshareParticipantsUpdated } from './actions';
-import { getAutoPinSetting, updateAutoPinnedParticipant } from './functions';
+import { setRemoteParticipantsWithScreenShare, virtualScreenshareParticipantsUpdated } from './actions.web';
+import { getAutoPinSetting, updateAutoPinnedParticipant } from './functions.web';
 
 StateListenerRegistry.register(
     /* selector */ state => state['features/base/participants'].sortedRemoteVirtualScreenshareParticipants,
@@ -60,7 +60,7 @@ StateListenerRegistry.register(
         }
 
         const oldScreenSharesOrder = store.getState()['features/video-layout'].remoteScreenShares || [];
-        const knownSharingParticipantIds = tracks.reduce((acc, track) => {
+        const knownSharingParticipantIds = tracks.reduce((acc: string[], track: ITrack) => {
             if (track.mediaType === 'video' && track.videoType === 'desktop') {
                 const skipTrack = getAutoPinSetting() === 'remote-only' && track.local;
 
@@ -76,11 +76,11 @@ StateListenerRegistry.register(
         // by looping through the known sharing participants and removing any
         // participant IDs which are no longer sharing.
         const newScreenSharesOrder = oldScreenSharesOrder.filter(
-            participantId => knownSharingParticipantIds.includes(participantId));
+            (participantId: string) => knownSharingParticipantIds.includes(participantId));
 
         // Make sure all new sharing participant get added to the end of the
         // known screen shares.
-        knownSharingParticipantIds.forEach(participantId => {
+        knownSharingParticipantIds.forEach((participantId: string) => {
             if (!newScreenSharesOrder.includes(participantId)) {
                 newScreenSharesOrder.push(participantId);
             }
diff --git a/react/features/video-quality/actions.js b/react/features/video-quality/actions.ts
similarity index 97%
rename from react/features/video-quality/actions.js
rename to react/features/video-quality/actions.ts
index 3eda4373e..ec422d6cc 100644
--- a/react/features/video-quality/actions.js
+++ b/react/features/video-quality/actions.ts
@@ -1,6 +1,4 @@
-// @flow
-
-import type { Dispatch } from 'redux';
+import { IStore } from '../app/types';
 
 import {
     SET_MAX_RECEIVER_VIDEO_QUALITY_FOR_LARGE_VIDEO,
@@ -125,7 +123,7 @@ export function setPreferredVideoQuality(preferredVideoQuality: number) {
  * @returns {void}
  */
 export function setVideoQuality(frameHeight: number) {
-    return (dispatch: Dispatch<any>) => {
+    return (dispatch: IStore['dispatch']) => {
         if (frameHeight < VIDEO_QUALITY_LEVELS.LOW) {
             logger.error(`Invalid frame height for video quality - ${frameHeight}`);
 
diff --git a/react/features/video-quality/functions.js b/react/features/video-quality/functions.ts
similarity index 96%
rename from react/features/video-quality/functions.js
rename to react/features/video-quality/functions.ts
index bd321afed..17a2ce18a 100644
--- a/react/features/video-quality/functions.js
+++ b/react/features/video-quality/functions.ts
@@ -29,7 +29,7 @@ export function getReceiverVideoQualityLevel(availableHeight: number, heightToLe
  * @returns {Map<number, number>|undefined} - A mapping of minimal thumbnail height required for given quality level or
  * {@code undefined} if the map contains invalid values.
  */
-export function validateMinHeightForQualityLvl(minHeightForQualityLvl) {
+export function validateMinHeightForQualityLvl(minHeightForQualityLvl?: { [key: number]: string; }) {
     if (typeof minHeightForQualityLvl !== 'object'
         || Object.keys(minHeightForQualityLvl).map(lvl => Number(lvl))
             .find(lvl => lvl === null || isNaN(lvl) || lvl < 0)) {
@@ -51,7 +51,7 @@ export function validateMinHeightForQualityLvl(minHeightForQualityLvl) {
 
     for (const level of levelsSorted) {
         const configQuality = minHeightForQualityLvl[level];
-        const appQuality = CFG_LVL_TO_APP_QUALITY_LVL[configQuality];
+        const appQuality = CFG_LVL_TO_APP_QUALITY_LVL[configQuality as keyof typeof CFG_LVL_TO_APP_QUALITY_LVL];
 
         if (!appQuality) {
             return undefined;
diff --git a/react/features/video-quality/middleware.js b/react/features/video-quality/middleware.ts
similarity index 85%
rename from react/features/video-quality/middleware.js
rename to react/features/video-quality/middleware.ts
index 60ae11e19..ac20832cb 100644
--- a/react/features/video-quality/middleware.js
+++ b/react/features/video-quality/middleware.ts
@@ -1,8 +1,6 @@
-// @flow
-
-import { CONFERENCE_JOINED } from '../base/conference';
-import { SET_CONFIG } from '../base/config';
-import { MiddlewareRegistry } from '../base/redux';
+import { CONFERENCE_JOINED } from '../base/conference/actionTypes';
+import { SET_CONFIG } from '../base/config/actionTypes';
+import MiddlewareRegistry from '../base/redux/MiddlewareRegistry';
 
 import { setPreferredVideoQuality } from './actions';
 import logger from './logger';
@@ -24,7 +22,7 @@ MiddlewareRegistry.register(({ dispatch, getState }) => next => action => {
             const { resolution } = getState()['features/base/config'];
 
             if (typeof resolution !== 'undefined') {
-                dispatch(setPreferredVideoQuality(Number.parseInt(resolution, 10)));
+                dispatch(setPreferredVideoQuality(Number.parseInt(`${resolution}`, 10)));
                 logger.info(`Configured preferred receiver video frame height to: ${resolution}`);
             }
         }
diff --git a/react/features/video-quality/selector.js b/react/features/video-quality/selector.ts
similarity index 64%
rename from react/features/video-quality/selector.js
rename to react/features/video-quality/selector.ts
index d873092d5..95647acf8 100644
--- a/react/features/video-quality/selector.js
+++ b/react/features/video-quality/selector.ts
@@ -1,4 +1,4 @@
-// @flow
+import { IReduxState } from '../app/types';
 
 /**
  * Selects the thumbnail height to the quality level mapping from the config.
@@ -6,6 +6,6 @@
  * @param {Object} state - The redux state.
  * @returns {Map<number,number>}
  */
-export function getMinHeightForQualityLvlMap(state: Object): Map<number, number> {
+export function getMinHeightForQualityLvlMap(state: IReduxState): Map<number, number> {
     return state['features/video-quality'].minHeightForQualityLvl;
 }
diff --git a/react/features/video-quality/subscriber.js b/react/features/video-quality/subscriber.ts
similarity index 94%
rename from react/features/video-quality/subscriber.js
rename to react/features/video-quality/subscriber.ts
index 2b70029fc..5560f2062 100644
--- a/react/features/video-quality/subscriber.js
+++ b/react/features/video-quality/subscriber.ts
@@ -1,26 +1,30 @@
-/* global APP */
-
 import debounce from 'lodash/debounce';
 
-import { _handleParticipantError } from '../base/conference';
-import { getSourceNameSignalingFeatureFlag } from '../base/config';
-import { MEDIA_TYPE } from '../base/media';
-import { getLocalParticipant } from '../base/participants';
-import { StateListenerRegistry } from '../base/redux';
-import { getRemoteScreenSharesSourceNames, getTrackSourceNameByMediaTypeAndParticipant } from '../base/tracks';
-import { reportError } from '../base/util';
+import { IStore } from '../app/types';
+import { _handleParticipantError } from '../base/conference/functions';
+import { getSourceNameSignalingFeatureFlag } from '../base/config/functions';
+import { MEDIA_TYPE } from '../base/media/constants';
+import { getLocalParticipant } from '../base/participants/functions';
+import StateListenerRegistry from '../base/redux/StateListenerRegistry';
+import {
+    getRemoteScreenSharesSourceNames,
+    getTrackSourceNameByMediaTypeAndParticipant
+} from '../base/tracks/functions';
+import { reportError } from '../base/util/helpers';
 import {
     getActiveParticipantsIds,
     getScreenshareFilmstripParticipantId,
     isTopPanelEnabled
+
+    // @ts-ignore
 } from '../filmstrip/functions';
+import { LAYOUTS } from '../video-layout/constants';
 import {
-    LAYOUTS,
     getVideoQualityForLargeVideo,
     getVideoQualityForResizableFilmstripThumbnails,
     getVideoQualityForStageThumbnails,
     shouldDisplayTileView
-} from '../video-layout';
+} from '../video-layout/functions';
 import { getCurrentLayout, getVideoQualityForScreenSharingFilmstrip } from '../video-layout/functions.any';
 
 import {
@@ -301,7 +305,7 @@ StateListenerRegistry.register(
  * @param {number} preferred - The user preferred max frame height.
  * @returns {void}
  */
-function _setSenderVideoConstraint(preferred, { getState }) {
+function _setSenderVideoConstraint(preferred: number, { getState }: IStore) {
     const state = getState();
     const { conference } = state['features/base/conference'];
 
@@ -311,7 +315,7 @@ function _setSenderVideoConstraint(preferred, { getState }) {
 
     logger.info(`Setting sender resolution to ${preferred}`);
     conference.setSenderVideoConstraint(preferred)
-        .catch(error => {
+        .catch((error: any) => {
             _handleParticipantError(error);
             reportError(error, `Changing sender resolution to ${preferred} failed.`);
         });
@@ -323,7 +327,7 @@ function _setSenderVideoConstraint(preferred, { getState }) {
  * @param {*} store - The redux store.
  * @returns {void}
  */
-function _updateReceiverVideoConstraints({ getState }) {
+function _updateReceiverVideoConstraints({ getState }: IStore) {
     const state = getState();
     const { conference } = state['features/base/conference'];
 
@@ -339,7 +343,7 @@ function _updateReceiverVideoConstraints({ getState }) {
         maxReceiverVideoQualityForScreenSharingFilmstrip,
         preferredVideoQuality
     } = state['features/video-quality'];
-    const { participantId: largeVideoParticipantId } = state['features/large-video'];
+    const { participantId: largeVideoParticipantId = '' } = state['features/large-video'];
     const maxFrameHeightForTileView = Math.min(maxReceiverVideoQualityForTileView, preferredVideoQuality);
     const maxFrameHeightForStageFilmstrip = Math.min(maxReceiverVideoQualityForStageFilmstrip, preferredVideoQuality);
     const maxFrameHeightForVerticalFilmstrip
@@ -352,20 +356,20 @@ function _updateReceiverVideoConstraints({ getState }) {
     const { visibleRemoteParticipants } = state['features/filmstrip'];
     const tracks = state['features/base/tracks'];
     const sourceNameSignaling = getSourceNameSignalingFeatureFlag(state);
-    const localParticipantId = getLocalParticipant(state).id;
+    const localParticipantId = getLocalParticipant(state)?.id;
     const activeParticipantsIds = getActiveParticipantsIds(state);
     const screenshareFilmstripParticipantId = isTopPanelEnabled(state) && getScreenshareFilmstripParticipantId(state);
 
-    const receiverConstraints = {
+    const receiverConstraints: any = {
         constraints: {},
         defaultConstraints: { 'maxHeight': VIDEO_QUALITY_LEVELS.NONE },
         lastN
     };
 
-    let remoteScreenSharesSourceNames;
-    let visibleRemoteTrackSourceNames = [];
-    let largeVideoSourceName;
-    let activeParticipantsSources = [];
+    let remoteScreenSharesSourceNames: string[];
+    let visibleRemoteTrackSourceNames: string[] = [];
+    let largeVideoSourceName: string | undefined;
+    let activeParticipantsSources: string[] = [];
 
     if (sourceNameSignaling) {
         receiverConstraints.onStageSources = [];
@@ -390,7 +394,7 @@ function _updateReceiverVideoConstraints({ getState }) {
         }
 
         if (activeParticipantsIds?.length > 0) {
-            activeParticipantsIds.forEach(participantId => {
+            activeParticipantsIds.forEach((participantId: string) => {
                 let sourceName;
 
                 if (remoteScreenSharesSourceNames.includes(participantId)) {
@@ -491,7 +495,7 @@ function _updateReceiverVideoConstraints({ getState }) {
 
     try {
         conference.setReceiverConstraints(receiverConstraints);
-    } catch (error) {
+    } catch (error: any) {
         _handleParticipantError(error);
         reportError(error, `Failed to set receiver video constraints ${JSON.stringify(receiverConstraints)}`);
     }