diff --git a/react/features/base/conference/reducer.ts b/react/features/base/conference/reducer.ts
index 361c0c6b1..3d95bb856 100644
--- a/react/features/base/conference/reducer.ts
+++ b/react/features/base/conference/reducer.ts
@@ -44,9 +44,13 @@ export interface IJitsiConference {
     addTrack: Function;
     getBreakoutRooms: Function;
     getLocalTracks: Function;
+    grantOwner: Function;
     isAVModerationSupported: Function;
     isEndConferenceSupported: Function;
     isLobbySupported: Function;
+    kickParticipant: Function;
+    muteParticipant: Function;
+    on: Function;
     removeTrack: Function;
     sendCommand: Function;
     sendEndpointMessage: Function;
diff --git a/react/features/base/config/configType.ts b/react/features/base/config/configType.ts
index 93636905d..9930bef56 100644
--- a/react/features/base/config/configType.ts
+++ b/react/features/base/config/configType.ts
@@ -67,7 +67,7 @@ type ButtonsWithNotifyClick = 'camera' |
     'add-passcode' |
     '__end';
 
-type Sounds = 'ASKED_TO_UNMUTE_SOUND' |
+export type Sounds = 'ASKED_TO_UNMUTE_SOUND' |
     'E2EE_OFF_SOUND' |
     'E2EE_ON_SOUND' |
     'INCOMING_MSG_SOUND' |
diff --git a/react/features/base/participants/actions.ts b/react/features/base/participants/actions.ts
index 258ce24b3..8357734e7 100644
--- a/react/features/base/participants/actions.ts
+++ b/react/features/base/participants/actions.ts
@@ -1,6 +1,4 @@
-import { Dispatch } from 'redux';
-
-// @ts-ignore
+import { IStore } from '../../app/types';
 import { showNotification } from '../../notifications/actions';
 import { NOTIFICATION_TIMEOUT_TYPE } from '../../notifications/constants';
 import { set } from '../redux/functions';
@@ -115,7 +113,7 @@ export function kickParticipant(id: string) {
  * @returns {Function}
  */
 export function localParticipantConnectionStatusChanged(connectionStatus: string) {
-    return (dispatch: Dispatch, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         const participant = getLocalParticipant(getState);
 
         if (participant) {
@@ -135,7 +133,7 @@ export function localParticipantConnectionStatusChanged(connectionStatus: string
  * @returns {Function}
  */
 export function localParticipantIdChanged(id: string) {
-    return (dispatch: Dispatch, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         const participant = getLocalParticipant(getState);
 
         if (participant) {
@@ -171,7 +169,7 @@ export function localParticipantJoined(participant: Participant = { id: '' }) {
  * @returns {Function}
  */
 export function localParticipantLeft() {
-    return (dispatch: Dispatch, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         const participant = getLocalParticipant(getState);
 
         if (participant) {
@@ -201,7 +199,7 @@ export function localParticipantLeft() {
  * @returns {Function}
  */
 export function localParticipantRoleChanged(role: string) {
-    return (dispatch: Dispatch, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         const participant = getLocalParticipant(getState);
 
         if (participant) {
@@ -280,7 +278,7 @@ export function participantJoined(participant: Participant) {
             'A remote participant must be associated with a JitsiConference!');
     }
 
-    return (dispatch: Dispatch, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         // A remote participant is only expected to join in a joined or joining
         // conference. The following check is really necessary because a
         // JitsiConference may have moved into leaving but may still manage to
@@ -310,7 +308,7 @@ export function participantJoined(participant: Participant) {
 * }}
 */
 export function updateRemoteParticipantFeatures(jitsiParticipant: any) {
-    return (dispatch: Dispatch, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         if (!jitsiParticipant) {
             return;
         }
@@ -508,7 +506,7 @@ export function participantUpdated(participant: Participant = { id: '' }) {
  * @returns {Promise}
  */
 export function participantMutedUs(participant: any, track: any) {
-    return (dispatch: Dispatch, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         if (!participant) {
             return;
         }
@@ -532,7 +530,7 @@ export function participantMutedUs(participant: any, track: any) {
  * @returns {Function}
  */
 export function createVirtualScreenshareParticipant(sourceName: string, local: boolean) {
-    return (dispatch: Dispatch<any>, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         const state = getState();
         const ownerId = getVirtualScreenshareParticipantOwnerId(sourceName);
         const ownerName = getParticipantDisplayName(state, ownerId);
@@ -555,7 +553,7 @@ export function createVirtualScreenshareParticipant(sourceName: string, local: b
  * @returns {Promise}
  */
 export function participantKicked(kicker: any, kicked: any) {
-    return (dispatch: Dispatch<any>, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
 
         dispatch({
             type: PARTICIPANT_KICKED,
diff --git a/react/features/base/participants/sounds.js b/react/features/base/participants/sounds.ts
similarity index 100%
rename from react/features/base/participants/sounds.js
rename to react/features/base/participants/sounds.ts
diff --git a/react/features/base/participants/subscriber.js b/react/features/base/participants/subscriber.ts
similarity index 85%
rename from react/features/base/participants/subscriber.js
rename to react/features/base/participants/subscriber.ts
index 68f21fc82..eeb8e2770 100644
--- a/react/features/base/participants/subscriber.js
+++ b/react/features/base/participants/subscriber.ts
@@ -1,13 +1,12 @@
-// @flow
-
 import _ from 'lodash';
 
-import { getCurrentConference } from '../conference';
+import { IStore } from '../../app/types';
+import { getCurrentConference } from '../conference/functions';
 import {
     getMultipleVideoSendingSupportFeatureFlag,
     getMultipleVideoSupportFeatureFlag
 } from '../config/functions.any';
-import { StateListenerRegistry } from '../redux';
+import StateListenerRegistry from '../redux/StateListenerRegistry';
 
 import { createVirtualScreenshareParticipant, participantLeft } from './actions';
 
@@ -22,7 +21,7 @@ StateListenerRegistry.register(
  * @param {*} store - The redux store.
  * @returns {void}
  */
-function _updateScreenshareParticipants({ getState, dispatch }) {
+function _updateScreenshareParticipants({ getState, dispatch }: IStore) {
     const state = getState();
 
     if (!getMultipleVideoSupportFeatureFlag(state)) {
@@ -36,9 +35,9 @@ function _updateScreenshareParticipants({ getState, dispatch }) {
 
     let newLocalSceenshareSourceName;
 
-    const currentScreenshareSourceNames = tracks.reduce((acc, track) => {
+    const currentScreenshareSourceNames = tracks.reduce((acc: string[], track) => {
         if (track.videoType === 'desktop' && !track.jitsiTrack.isMuted()) {
-            const sourceName = track.jitsiTrack.getSourceName();
+            const sourceName: string = track.jitsiTrack.getSourceName();
 
             if (track.local) {
                 newLocalSceenshareSourceName = sourceName;
diff --git a/react/features/base/participants/types.ts b/react/features/base/participants/types.ts
index bf699eac5..6e57f703f 100644
--- a/react/features/base/participants/types.ts
+++ b/react/features/base/participants/types.ts
@@ -15,15 +15,18 @@ export interface Participant {
     isFakeParticipant?: boolean;
     isJigasi?: boolean;
     isLocalScreenShare?: boolean;
+    isReplaced?: boolean;
     isReplacing?: number;
     isVirtualScreenshareParticipant?: boolean;
     loadableAvatarUrl?: string;
     loadableAvatarUrlUseCORS?: boolean;
     local?: boolean;
+    localRecording?: string;
     name?: string;
     pinned?: boolean;
     presence?: string;
     raisedHandTimestamp?: number;
+    region?: string;
     remoteControlSessionStatus?: boolean;
     role?: string;
     supportsRemoteControl?: boolean;
diff --git a/react/features/base/popover/functions.web.js b/react/features/base/popover/functions.web.ts
similarity index 86%
rename from react/features/base/popover/functions.web.js
rename to react/features/base/popover/functions.web.ts
index 804ec1d0e..fd653aea8 100644
--- a/react/features/base/popover/functions.web.js
+++ b/react/features/base/popover/functions.web.ts
@@ -1,67 +1,65 @@
-// @flow
-
 const LEFT_RIGHT_OFFSET = 25;
 const TOP_BOTTOM_OFFSET = 20;
 
-const getLeftAlignedStyle = bounds => {
+const getLeftAlignedStyle = (bounds: DOMRect) => {
     return {
         position: 'fixed',
         right: `${window.innerWidth - bounds.x + LEFT_RIGHT_OFFSET}px`
     };
 };
 
-const getRightAlignedStyle = bounds => {
+const getRightAlignedStyle = (bounds: DOMRect) => {
     return {
         position: 'fixed',
         left: `${bounds.x + bounds.width + LEFT_RIGHT_OFFSET}px`
     };
 };
 
-const getTopAlignedStyle = bounds => {
+const getTopAlignedStyle = (bounds: DOMRect) => {
     return {
         position: 'fixed',
         bottom: `${window.innerHeight - bounds.y + TOP_BOTTOM_OFFSET}px`
     };
 };
 
-const getBottomAlignedStyle = bounds => {
+const getBottomAlignedStyle = (bounds: DOMRect) => {
     return {
         position: 'fixed',
         top: `${bounds.y + bounds.height + TOP_BOTTOM_OFFSET}px`
     };
 };
 
-const getLeftRightStartAlign = (bounds, size) => {
+const getLeftRightStartAlign = (bounds: DOMRect, size: DOMRectReadOnly) => {
     return {
         top: `${Math.min(bounds.y + 15, window.innerHeight - size.height - 20)}px`
     };
 };
 
-const getLeftRightMidAlign = (bounds, size) => {
+const getLeftRightMidAlign = (bounds: DOMRect, size: DOMRectReadOnly) => {
     return {
         bottom: `${window.innerHeight - bounds.y - bounds.height - (size.height / 2)}px`
     };
 };
 
-const getLeftRightEndAlign = (bounds, size) => {
+const getLeftRightEndAlign = (bounds: DOMRect, size: DOMRectReadOnly) => {
     return {
         bottom: `${Math.min(window.innerHeight - bounds.y - bounds.height, window.innerHeight - size.height)}px`
     };
 };
 
-const getTopBotStartAlign = bounds => {
+const getTopBotStartAlign = (bounds: DOMRect) => {
     return {
         right: `${window.innerWidth - bounds.x + 10}px`
     };
 };
 
-const getTopBotMidAlign = (bounds, size) => {
+const getTopBotMidAlign = (bounds: DOMRect, size: DOMRectReadOnly) => {
     return {
         right: `${window.innerWidth - bounds.x - (size.width / 2)}px`
     };
 };
 
-const getTopBotEndAlign = bounds => {
+const getTopBotEndAlign = (bounds: DOMRect) => {
     return {
         left: `${bounds.x + bounds.width + 10}px`
     };
diff --git a/react/features/base/premeeting/functions.js b/react/features/base/premeeting/functions.ts
similarity index 94%
rename from react/features/base/premeeting/functions.js
rename to react/features/base/premeeting/functions.ts
index ddedbb7e8..6c2791486 100644
--- a/react/features/base/premeeting/functions.js
+++ b/react/features/base/premeeting/functions.ts
@@ -1,10 +1,8 @@
-// @flow
-
 import { findIndex } from 'lodash';
 
-import { CONNECTION_TYPE } from './constants';
+import { IState } from '../../app/types';
 
-declare var interfaceConfig: Object;
+import { CONNECTION_TYPE } from './constants';
 
 const LOSS_AUDIO_THRESHOLDS = [ 0.33, 0.05 ];
 const LOSS_VIDEO_THRESHOLDS = [ 0.33, 0.1, 0.05 ];
@@ -90,15 +88,15 @@ export function calculateAvatarDimensions(height: number) {
  *
  * @returns {number}
  */
-function _getLevel(thresholds, value, descending = true) {
+function _getLevel(thresholds: number[], value: number, descending = true) {
     let predicate;
 
     if (descending) {
-        predicate = function(threshold) {
+        predicate = function(threshold: number) {
             return value > threshold;
         };
     } else {
-        predicate = function(threshold) {
+        predicate = function(threshold: number) {
             return value < threshold;
         };
     }
@@ -123,7 +121,8 @@ function _getLevel(thresholds, value, descending = true) {
  *   connectionDetails: string[]
  * }}
  */
-function _getConnectionDataFromTestResults({ fractionalLoss: l, throughput: t }) {
+function _getConnectionDataFromTestResults({ fractionalLoss: l, throughput: t }:
+    { fractionalLoss: number; throughput: number; }) {
     const loss = {
         audioQuality: _getLevel(LOSS_AUDIO_THRESHOLDS, l),
         videoQuality: _getLevel(LOSS_VIDEO_THRESHOLDS, l)
@@ -192,7 +191,7 @@ function _getConnectionDataFromTestResults({ fractionalLoss: l, throughput: t })
  *   connectionDetails: string[]
  * }}
  */
-export function getConnectionData(state: Object) {
+export function getConnectionData(state: IState) {
     const { precallTestResults } = state['features/prejoin'];
 
     if (precallTestResults) {
diff --git a/react/features/base/premeeting/logger.js b/react/features/base/premeeting/logger.ts
similarity index 91%
rename from react/features/base/premeeting/logger.js
rename to react/features/base/premeeting/logger.ts
index 1d09c1b7a..81a80b318 100644
--- a/react/features/base/premeeting/logger.js
+++ b/react/features/base/premeeting/logger.ts
@@ -1,5 +1,3 @@
-// @flow
-
 import { getLogger } from '../logging/functions';
 
 export default getLogger('features/base/premeeting');
diff --git a/react/features/base/react/Platform.native.js b/react/features/base/react/Platform.native.ts
similarity index 92%
rename from react/features/base/react/Platform.native.js
rename to react/features/base/react/Platform.native.ts
index 2c5130848..1710b20d3 100644
--- a/react/features/base/react/Platform.native.js
+++ b/react/features/base/react/Platform.native.ts
@@ -1,5 +1,3 @@
-/* @flow */
-
 // Re-export react-native's Platform because we want to provide a minimal
 // equivalent on Web.
 import { Platform } from 'react-native';
diff --git a/react/features/base/react/functions.js b/react/features/base/react/functions.ts
similarity index 76%
rename from react/features/base/react/functions.js
rename to react/features/base/react/functions.ts
index 1180038c3..df627fb70 100644
--- a/react/features/base/react/functions.js
+++ b/react/features/base/react/functions.ts
@@ -1,11 +1,9 @@
-// @flow
-
 /**
  * Returns the field value in a platform generic way.
  *
  * @param {Object | string} fieldParameter - The parameter passed through the change event function.
  * @returns {string}
  */
-export function getFieldValue(fieldParameter: Object | string) {
+export function getFieldValue(fieldParameter: { target: { value: string; }; } | string) {
     return typeof fieldParameter === 'string' ? fieldParameter : fieldParameter?.target?.value;
 }
diff --git a/react/features/base/react/logger.js b/react/features/base/react/logger.ts
similarity index 90%
rename from react/features/base/react/logger.js
rename to react/features/base/react/logger.ts
index 18ff002fa..71e0a0f7f 100644
--- a/react/features/base/react/logger.js
+++ b/react/features/base/react/logger.ts
@@ -1,5 +1,3 @@
-// @flow
-
 import { getLogger } from '../logging/functions';
 
 export default getLogger('features/base/react');
diff --git a/react/features/base/redux/MiddlewareRegistry.ts b/react/features/base/redux/MiddlewareRegistry.ts
index 8a97085b9..cb107e0fd 100644
--- a/react/features/base/redux/MiddlewareRegistry.ts
+++ b/react/features/base/redux/MiddlewareRegistry.ts
@@ -1,6 +1,6 @@
 import { applyMiddleware, Middleware } from 'redux';
 
-import { IState } from '../../app/types';
+import { IState, IStore } from '../../app/types';
 
 /**
  * A registry for Redux middleware, allowing features to register their
@@ -42,7 +42,7 @@ class MiddlewareRegistry {
      * @param {Middleware} middleware - A Redux middleware.
      * @returns {void}
      */
-    register(middleware: Middleware<any, IState>) {
+    register(middleware: Middleware<any, IState, IStore['dispatch']>) {
         this._elements.push(middleware);
     }
 }
diff --git a/react/features/base/redux/StateListenerRegistry.ts b/react/features/base/redux/StateListenerRegistry.ts
index d4d5fb632..d8e27e69a 100644
--- a/react/features/base/redux/StateListenerRegistry.ts
+++ b/react/features/base/redux/StateListenerRegistry.ts
@@ -1,6 +1,6 @@
 import { Store } from 'redux';
 
-import { IState } from '../../app/types';
+import { IState, IStore } from '../../app/types';
 
 import { equals } from './functions';
 import logger from './logger';
@@ -20,7 +20,7 @@ import logger from './logger';
  * Immutable!
  */
 type Listener
-    = (selection: any, store: Store<any, any>, prevSelection: any) => void;
+    = (selection: any, store: IStore, prevSelection: any) => void;
 
 /**
  * The type selector supported for registration with
diff --git a/react/features/base/responsive-ui/actions.js b/react/features/base/responsive-ui/actions.ts
similarity index 89%
rename from react/features/base/responsive-ui/actions.js
rename to react/features/base/responsive-ui/actions.ts
index 1f738fd8a..1232d0bcd 100644
--- a/react/features/base/responsive-ui/actions.js
+++ b/react/features/base/responsive-ui/actions.ts
@@ -1,8 +1,6 @@
-// @flow
-
 import { batch } from 'react-redux';
-import type { Dispatch } from 'redux';
 
+import { IStore } from '../../app/types';
 import { CHAT_SIZE } from '../../chat/constants';
 import { getParticipantsPaneOpen } from '../../participants-pane/functions';
 import theme from '../components/themes/participantsPaneTheme.json';
@@ -35,7 +33,7 @@ const REDUCED_UI_THRESHOLD = 300;
  * @returns {Object}
  */
 export function clientResized(clientWidth: number, clientHeight: number) {
-    return (dispatch: Dispatch<any>, getState: Function) => {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         let availableWidth = clientWidth;
 
         if (navigator.product !== 'ReactNative') {
@@ -74,8 +72,8 @@ export function clientResized(clientWidth: number, clientHeight: number) {
  *     aspectRatio: Symbol
  * }}
  */
-export function setAspectRatio(width: number, height: number): Function {
-    return (dispatch: Dispatch<any>, getState: Function) => {
+export function setAspectRatio(width: number, height: number) {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         // Don't change the aspect ratio if width and height are the same, that
         // is, if we transition to a 1:1 aspect ratio.
         if (width !== height) {
@@ -104,8 +102,8 @@ export function setAspectRatio(width: number, height: number): Function {
  *     reducedUI: boolean
  * }}
  */
-export function setReducedUI(width: number, height: number): Function {
-    return (dispatch: Dispatch<any>, getState: Function) => {
+export function setReducedUI(width: number, height: number) {
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) => {
         const reducedUI = Math.min(width, height) < REDUCED_UI_THRESHOLD;
 
         if (reducedUI !== getState()['features/base/responsive-ui'].reducedUI) {
@@ -139,7 +137,7 @@ export function setParticipantContextMenuOpen(isOpen: boolean) {
  *    insets: Object
  * }}
  */
-export function setSafeAreaInsets(insets) {
+export function setSafeAreaInsets(insets: Object) {
     return {
         type: SAFE_AREA_INSETS_CHANGED,
         insets
diff --git a/react/features/base/responsive-ui/middleware.native.js b/react/features/base/responsive-ui/middleware.native.ts
similarity index 91%
rename from react/features/base/responsive-ui/middleware.native.js
rename to react/features/base/responsive-ui/middleware.native.ts
index a7b9bbd25..a3e89bfc7 100644
--- a/react/features/base/responsive-ui/middleware.native.js
+++ b/react/features/base/responsive-ui/middleware.native.ts
@@ -1,6 +1,4 @@
-// @flow
-
-import { MiddlewareRegistry } from '../../base/redux';
+import MiddlewareRegistry from '../redux/MiddlewareRegistry';
 
 import { CLIENT_RESIZED } from './actionTypes';
 import { setAspectRatio, setReducedUI } from './actions';
diff --git a/react/features/base/responsive-ui/middleware.web.js b/react/features/base/responsive-ui/middleware.web.ts
similarity index 78%
rename from react/features/base/responsive-ui/middleware.web.js
rename to react/features/base/responsive-ui/middleware.web.ts
index 9d5109e56..b1b7932b8 100644
--- a/react/features/base/responsive-ui/middleware.web.js
+++ b/react/features/base/responsive-ui/middleware.web.ts
@@ -1,14 +1,13 @@
-// @flow
-
-import { APP_WILL_MOUNT, APP_WILL_UNMOUNT } from '../../base/app';
-import { MiddlewareRegistry } from '../../base/redux';
+import { IStore } from '../../app/types';
+import { APP_WILL_MOUNT, APP_WILL_UNMOUNT } from '../app/actionTypes';
+import MiddlewareRegistry from '../redux/MiddlewareRegistry';
 
 import { clientResized } from './actions';
 
 /**
  * Dimensions change handler.
  */
-let handler;
+let handler: undefined | ((this: Window, ev: UIEvent) => any);
 
 /**
  * Middleware that handles window dimension changes.
@@ -42,7 +41,7 @@ MiddlewareRegistry.register(store => next => action => {
  * @private
  * @returns {void}
  */
-function _appWillMount(store) {
+function _appWillMount(store: IStore) {
     handler = () => {
         const {
             innerHeight,
@@ -63,7 +62,7 @@ function _appWillMount(store) {
  * @returns {void}
  */
 function _appWillUnmount() {
-    window.removeEventListener('resize', handler);
+    handler && window.removeEventListener('resize', handler);
 
     handler = undefined;
 }
diff --git a/react/features/base/sounds/actions.js b/react/features/base/sounds/actions.ts
similarity index 94%
rename from react/features/base/sounds/actions.js
rename to react/features/base/sounds/actions.ts
index 4584bc575..1935ae933 100644
--- a/react/features/base/sounds/actions.js
+++ b/react/features/base/sounds/actions.ts
@@ -1,5 +1,6 @@
-// @flow
-
+/* eslint-disable lines-around-comment */
+import { Sounds } from '../config/configType';
+// @ts-ignore
 import type { AudioElement } from '../media';
 
 import {
@@ -10,6 +11,7 @@ import {
     STOP_SOUND,
     UNREGISTER_SOUND
 } from './actionTypes';
+// @ts-ignore
 import { getSoundsPath } from './functions';
 import { getDisabledSounds } from './functions.any';
 
@@ -70,7 +72,7 @@ export function playSound(soundId: string): Object {
     return (dispatch: Function, getState: Function) => {
         const disabledSounds = getDisabledSounds(getState());
 
-        if (!disabledSounds.includes(soundId) && !disabledSounds.find(id => soundId.startsWith(id))) {
+        if (!disabledSounds.includes(soundId as Sounds) && !disabledSounds.find(id => soundId.startsWith(id))) {
             dispatch({
                 type: PLAY_SOUND,
                 soundId
diff --git a/react/features/base/sounds/functions.any.js b/react/features/base/sounds/functions.any.ts
similarity index 71%
rename from react/features/base/sounds/functions.any.js
rename to react/features/base/sounds/functions.any.ts
index 251fa3a84..ddb586657 100644
--- a/react/features/base/sounds/functions.any.js
+++ b/react/features/base/sounds/functions.any.ts
@@ -1,4 +1,4 @@
-// @flow
+import { IState } from '../../app/types';
 
 /**
  * Selector for retrieving the disabled sounds array.
@@ -6,6 +6,6 @@
  * @param {Object} state - The Redux state.
  * @returns {Array<string>} - The disabled sound id's array.
  */
-export function getDisabledSounds(state: Object) {
+export function getDisabledSounds(state: IState) {
     return state['features/base/config'].disabledSounds || [];
 }
diff --git a/react/features/base/testing/logger.js b/react/features/base/testing/logger.ts
similarity index 91%
rename from react/features/base/testing/logger.js
rename to react/features/base/testing/logger.ts
index a762f52a9..1698fd2d2 100644
--- a/react/features/base/testing/logger.js
+++ b/react/features/base/testing/logger.ts
@@ -1,5 +1,3 @@
-// @flow
-
 import { getLogger } from '../logging/functions';
 
 export default getLogger('features/base/testing');
diff --git a/react/features/base/testing/middleware.js b/react/features/base/testing/middleware.ts
similarity index 85%
rename from react/features/base/testing/middleware.js
rename to react/features/base/testing/middleware.ts
index f13ade563..62343f643 100644
--- a/react/features/base/testing/middleware.js
+++ b/react/features/base/testing/middleware.ts
@@ -1,10 +1,10 @@
-// @flow
-
+import { IStore } from '../../app/types';
 import { CONFERENCE_JOIN_IN_PROGRESS } from '../conference/actionTypes';
-import { SET_CONFIG } from '../config';
+import { IJitsiConference } from '../conference/reducer';
+import { SET_CONFIG } from '../config/actionTypes';
 import { JitsiConferenceEvents } from '../lib-jitsi-meet';
-import { MiddlewareRegistry } from '../redux';
-import { getJitsiMeetGlobalNS } from '../util';
+import MiddlewareRegistry from '../redux/MiddlewareRegistry';
+import { getJitsiMeetGlobalNS } from '../util/helpers';
 
 import { setConnectionState } from './actions';
 import {
@@ -51,7 +51,7 @@ MiddlewareRegistry.register(store => next => action => {
  * @private
  * @returns {void}
  */
-function _bindConferenceConnectionListener(conference, { dispatch }) {
+function _bindConferenceConnectionListener(conference: IJitsiConference, { dispatch }: IStore) {
 
     conference.on(
         JitsiConferenceEvents.CONNECTION_ESTABLISHED,
@@ -70,11 +70,11 @@ function _bindConferenceConnectionListener(conference, { dispatch }) {
 /**
  * Binds all the helper functions needed by torture.
  *
- * @param {Store} store - The redux store.
+ * @param {IStore} store - The redux store.
  * @private
  * @returns {void}
  */
-function _bindTortureHelpers(store) {
+function _bindTortureHelpers(store: IStore) {
     const { getState } = store;
 
     // We bind helpers only if testing mode is enabled
@@ -100,7 +100,7 @@ function _bindTortureHelpers(store) {
  * @returns {void}
  * @private
  */
-function _onConnectionEvent(event, dispatch) {
+function _onConnectionEvent(event: string, dispatch: IStore['dispatch']) {
     switch (event) {
     case JitsiConferenceEvents.CONNECTION_ESTABLISHED:
     case JitsiConferenceEvents.CONNECTION_INTERRUPTED:
diff --git a/react/features/e2ee/actions.js b/react/features/e2ee/actions.ts
similarity index 99%
rename from react/features/e2ee/actions.js
rename to react/features/e2ee/actions.ts
index c3f17554d..0548c6a01 100644
--- a/react/features/e2ee/actions.js
+++ b/react/features/e2ee/actions.ts
@@ -1,5 +1,3 @@
-// @flow
-
 import {
     SET_EVERYONE_ENABLED_E2EE,
     SET_EVERYONE_SUPPORT_E2EE,
diff --git a/react/features/notifications/actions.js b/react/features/notifications/actions.ts
similarity index 83%
rename from react/features/notifications/actions.js
rename to react/features/notifications/actions.ts
index cff01969e..60dd8fa2e 100644
--- a/react/features/notifications/actions.js
+++ b/react/features/notifications/actions.ts
@@ -1,9 +1,8 @@
-// @flow
-
 import throttle from 'lodash/throttle';
-import type { Dispatch } from 'redux';
 
-import { NOTIFICATIONS_ENABLED, getFeatureFlag } from '../base/flags';
+import { IStore } from '../app/types';
+import { NOTIFICATIONS_ENABLED } from '../base/flags/constants';
+import { getFeatureFlag } from '../base/flags/functions';
 import { getParticipantCount } from '../base/participants/functions';
 
 import {
@@ -28,7 +27,11 @@ import {
  * @param {Object} notificationTimeouts - Config notification timeouts.
  * @returns {number}
  */
-function getNotificationTimeout(type: ?string, notificationTimeouts: ?Object) {
+function getNotificationTimeout(type?: string, notificationTimeouts?: {
+    long?: number;
+    medium?: number;
+    short?: number;
+}) {
     if (type === NOTIFICATION_TIMEOUT_TYPE.SHORT) {
         return notificationTimeouts?.short ?? NOTIFICATION_TIMEOUT.SHORT;
     } else if (type === NOTIFICATION_TIMEOUT_TYPE.MEDIUM) {
@@ -86,6 +89,19 @@ export function setNotificationsEnabled(enabled: boolean) {
     };
 }
 
+interface INotificationProps {
+    appearance?: string;
+    concatText?: boolean;
+    description?: string;
+    descriptionKey?: string;
+    icon?: string;
+    titleArguments?: {
+        [key: string]: string;
+    };
+    titleKey?: string;
+    uid?: string;
+}
+
 /**
  * Queues an error notification for display.
  *
@@ -93,7 +109,7 @@ export function setNotificationsEnabled(enabled: boolean) {
  * @param {string} type - Notification type.
  * @returns {Object}
  */
-export function showErrorNotification(props: Object, type: ?string) {
+export function showErrorNotification(props: INotificationProps, type?: string) {
     return showNotification({
         ...props,
         appearance: NOTIFICATION_TYPE.ERROR
@@ -107,17 +123,17 @@ export function showErrorNotification(props: Object, type: ?string) {
  * @param {string} type - Timeout type.
  * @returns {Function}
  */
-export function showNotification(props: Object = {}, type: ?string) {
-    return function(dispatch: Function, getState: Function) {
+export function showNotification(props: INotificationProps = {}, type?: string) {
+    return function(dispatch: IStore['dispatch'], getState: IStore['getState']) {
         const { disabledNotifications = [], notifications, notificationTimeouts } = getState()['features/base/config'];
         const enabledFlag = getFeatureFlag(getState(), NOTIFICATIONS_ENABLED, true);
 
         const shouldDisplay = enabledFlag
-            && !(disabledNotifications.includes(props.descriptionKey)
-                || disabledNotifications.includes(props.titleKey))
+            && !(disabledNotifications.includes(props.descriptionKey ?? '')
+                || disabledNotifications.includes(props.titleKey ?? ''))
             && (!notifications
-                || notifications.includes(props.descriptionKey)
-                || notifications.includes(props.titleKey));
+                || notifications.includes(props.descriptionKey ?? '')
+                || notifications.includes(props.titleKey ?? ''));
 
         if (shouldDisplay) {
             return dispatch({
@@ -137,7 +153,7 @@ export function showNotification(props: Object = {}, type: ?string) {
  * @param {string} type - Notification type.
  * @returns {Object}
  */
-export function showWarningNotification(props: Object, type: ?string) {
+export function showWarningNotification(props: INotificationProps, type?: string) {
 
     return showNotification({
         ...props,
@@ -152,7 +168,7 @@ export function showWarningNotification(props: Object, type: ?string) {
  * @param {string} type - Notification type.
  * @returns {Object}
  */
-export function showMessageNotification(props: Object, type: ?string) {
+export function showMessageNotification(props: INotificationProps, type?: string) {
     return showNotification({
         ...props,
         concatText: true,
@@ -169,7 +185,7 @@ export function showMessageNotification(props: Object, type: ?string) {
  * @private
  * @type {string[]}
  */
-let joinedParticipantsNames = [];
+let joinedParticipantsNames: string[] = [];
 
 /**
  * A throttled internal function that takes the internal list of participant
@@ -179,7 +195,7 @@ let joinedParticipantsNames = [];
  * @private
  * @type {Function}
  */
-const _throttledNotifyParticipantConnected = throttle((dispatch: Dispatch<any>, getState: Function) => {
+const _throttledNotifyParticipantConnected = throttle((dispatch: IStore['dispatch'], getState: IStore['getState']) => {
     const participantCount = getParticipantCount(getState());
 
     // Skip join notifications altogether for large meetings.
@@ -233,7 +249,7 @@ const _throttledNotifyParticipantConnected = throttle((dispatch: Dispatch<any>,
  * @private
  * @type {string[]}
  */
-let leftParticipantsNames = [];
+let leftParticipantsNames: string[] = [];
 
 /**
  * A throttled internal function that takes the internal list of participant
@@ -243,7 +259,7 @@ let leftParticipantsNames = [];
  * @private
  * @type {Function}
  */
-const _throttledNotifyParticipantLeft = throttle((dispatch: Dispatch<any>, getState: Function) => {
+const _throttledNotifyParticipantLeft = throttle((dispatch: IStore['dispatch'], getState: IStore['getState']) => {
     const participantCount = getParticipantCount(getState());
 
     // Skip left notifications altogether for large meetings.
@@ -301,7 +317,8 @@ const _throttledNotifyParticipantLeft = throttle((dispatch: Dispatch<any>, getSt
 export function showParticipantJoinedNotification(displayName: string) {
     joinedParticipantsNames.push(displayName);
 
-    return (dispatch: Dispatch<any>, getState: Function) => _throttledNotifyParticipantConnected(dispatch, getState);
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) =>
+        _throttledNotifyParticipantConnected(dispatch, getState);
 }
 
 /**
@@ -315,5 +332,6 @@ export function showParticipantJoinedNotification(displayName: string) {
 export function showParticipantLeftNotification(displayName: string) {
     leftParticipantsNames.push(displayName);
 
-    return (dispatch: Dispatch<any>, getState: Function) => _throttledNotifyParticipantLeft(dispatch, getState);
+    return (dispatch: IStore['dispatch'], getState: IStore['getState']) =>
+        _throttledNotifyParticipantLeft(dispatch, getState);
 }
diff --git a/react/features/notifications/components/web/NotificationsContainer.tsx b/react/features/notifications/components/web/NotificationsContainer.tsx
index ac0aab4a9..fbb71e153 100644
--- a/react/features/notifications/components/web/NotificationsContainer.tsx
+++ b/react/features/notifications/components/web/NotificationsContainer.tsx
@@ -184,11 +184,11 @@ class NotificationsContainer extends Component<Props> {
      * Emits an action to remove the notification from the redux store so it
      * stops displaying.
      *
-     * @param {number} uid - The id of the notification to be removed.
+     * @param {string} uid - The id of the notification to be removed.
      * @private
      * @returns {void}
      */
-    _onDismissed(uid: number) {
+    _onDismissed(uid: string) {
         const timeout = this._timeouts.get(`${uid}`);
 
         if (timeout) {
diff --git a/react/features/notifications/middleware.js b/react/features/notifications/middleware.ts
similarity index 90%
rename from react/features/notifications/middleware.js
rename to react/features/notifications/middleware.ts
index a7eafedbd..4a4e164e3 100644
--- a/react/features/notifications/middleware.js
+++ b/react/features/notifications/middleware.ts
@@ -1,16 +1,18 @@
-/* @flow */
-
-import { getCurrentConference } from '../base/conference';
+import { IState, IStore } from '../app/types';
+import { getCurrentConference } from '../base/conference/functions';
 import {
     PARTICIPANT_JOINED,
     PARTICIPANT_LEFT,
-    PARTICIPANT_ROLE,
-    PARTICIPANT_UPDATED,
+    PARTICIPANT_UPDATED
+} from '../base/participants/actionTypes';
+import { PARTICIPANT_ROLE } from '../base/participants/constants';
+import {
     getParticipantById,
     getParticipantDisplayName,
     getLocalParticipant
-} from '../base/participants';
-import { MiddlewareRegistry, StateListenerRegistry } from '../base/redux';
+} from '../base/participants/functions';
+import MiddlewareRegistry from '../base/redux/MiddlewareRegistry';
+import StateListenerRegistry from '../base/redux/StateListenerRegistry';
 import { PARTICIPANTS_PANE_OPEN } from '../participants-pane/actionTypes';
 
 import {
@@ -45,7 +47,7 @@ const timers = new Map();
  * @param {Function} dispatch - The Redux dispatch function.
  * @returns {void}
  */
-const createTimeoutId = (notification, dispatch) => {
+const createTimeoutId = (notification: { timeout: number; uid: string; }, dispatch: IStore['dispatch']) => {
     const {
         timeout,
         uid
@@ -66,7 +68,7 @@ const createTimeoutId = (notification, dispatch) => {
  * @param {Object} state - Global state.
  * @returns {Array<Object>} - Notifications state.
  */
-const getNotifications = state => {
+const getNotifications = (state: IState) => {
     const _visible = areThereNotifications(state);
     const { notifications } = state['features/notifications'];
 
@@ -80,7 +82,6 @@ const getNotifications = state => {
  * @returns {Function}
  */
 MiddlewareRegistry.register(store => next => action => {
-
     const { dispatch, getState } = store;
     const state = getState();
 
diff --git a/react/features/prejoin/reducer.ts b/react/features/prejoin/reducer.ts
index 7fb509c89..3d3bd11e2 100644
--- a/react/features/prejoin/reducer.ts
+++ b/react/features/prejoin/reducer.ts
@@ -48,7 +48,11 @@ export interface IPrejoinState {
     isDisplayNameRequired: boolean;
     joiningInProgress?: boolean;
     name: string;
-    precallTestResults?: Object;
+    precallTestResults?: {
+        fractionalLoss: number;
+        mediaConnectivity: boolean;
+        throughput: number;
+    };
     rawError: string;
     showJoinByPhoneDialog: boolean;
     showPrejoin: boolean;