diff --git a/src/components/structures/GenericDropdownMenu.tsx b/src/components/structures/GenericDropdownMenu.tsx
index e0fd3b7f9b6..06854768dba 100644
--- a/src/components/structures/GenericDropdownMenu.tsx
+++ b/src/components/structures/GenericDropdownMenu.tsx
@@ -97,6 +97,12 @@ type WithKeyFunction<T> = T extends Key
           toKey: (key: T) => Key;
       };
 
+export interface AdditionalOptionsProps {
+    menuDisplayed: boolean;
+    closeMenu: () => void;
+    openMenu: () => void;
+}
+
 type IProps<T> = WithKeyFunction<T> & {
     value: T;
     options: readonly GenericDropdownMenuOption<T>[] | readonly GenericDropdownMenuGroup<T>[];
@@ -105,11 +111,7 @@ type IProps<T> = WithKeyFunction<T> & {
     onOpen?: (ev: ButtonEvent) => void;
     onClose?: (ev: ButtonEvent) => void;
     className?: string;
-    AdditionalOptions?: FunctionComponent<{
-        menuDisplayed: boolean;
-        closeMenu: () => void;
-        openMenu: () => void;
-    }>;
+    AdditionalOptions?: FunctionComponent<AdditionalOptionsProps>;
 };
 
 export function GenericDropdownMenu<T>({
diff --git a/src/components/structures/ThreadPanel.tsx b/src/components/structures/ThreadPanel.tsx
index 8951cfcb910..792c97bc52e 100644
--- a/src/components/structures/ThreadPanel.tsx
+++ b/src/components/structures/ThreadPanel.tsx
@@ -117,7 +117,7 @@ export const ThreadPanelHeader: React.FC<{
     ) : null;
 
     const onMarkAllThreadsReadClick = React.useCallback(
-        (e) => {
+        (e: React.MouseEvent) => {
             PosthogTrackers.trackInteraction("WebThreadsMarkAllReadButton", e);
             if (!roomContext.room) {
                 logger.error("No room in context to mark all threads read");
diff --git a/src/components/structures/auth/Registration.tsx b/src/components/structures/auth/Registration.tsx
index 5ac49537c58..ede57677450 100644
--- a/src/components/structures/auth/Registration.tsx
+++ b/src/components/structures/auth/Registration.tsx
@@ -248,15 +248,20 @@ export default class Registration extends React.Component<IProps, IState> {
             logger.error("Failed to get login flows to check for SSO support", e);
         }
 
-        this.setState(({ flows }) => ({
-            matrixClient: cli,
-            ssoFlow,
-            oidcNativeFlow,
-            // if we are using oidc native we won't continue with flow discovery on HS
-            // so set an empty array to indicate flows are no longer loading
-            flows: oidcNativeFlow ? [] : flows,
-            busy: false,
-        }));
+        await new Promise<void>((resolve) => {
+            this.setState(
+                ({ flows }) => ({
+                    matrixClient: cli,
+                    ssoFlow,
+                    oidcNativeFlow,
+                    // if we are using oidc native we won't continue with flow discovery on HS
+                    // so set an empty array to indicate flows are no longer loading
+                    flows: oidcNativeFlow ? [] : flows,
+                    busy: false,
+                }),
+                resolve,
+            );
+        });
 
         // don't need to check with homeserver for login flows
         // since we are going to use OIDC native flow
diff --git a/src/components/views/avatars/BaseAvatar.tsx b/src/components/views/avatars/BaseAvatar.tsx
index d956c26da28..b35109f5d71 100644
--- a/src/components/views/avatars/BaseAvatar.tsx
+++ b/src/components/views/avatars/BaseAvatar.tsx
@@ -19,7 +19,7 @@ limitations under the License.
 
 import React, { forwardRef, useCallback, useContext, useEffect, useState } from "react";
 import classNames from "classnames";
-import { ClientEvent } from "matrix-js-sdk/src/matrix";
+import { ClientEvent, SyncState } from "matrix-js-sdk/src/matrix";
 import { Avatar } from "@vector-im/compound-web";
 
 import SettingsStore from "../../../settings/SettingsStore";
@@ -80,7 +80,7 @@ const useImageUrl = ({ url, urls }: { url?: string | null; urls?: string[] }): [
     }, [url, JSON.stringify(urls)]); // eslint-disable-line react-hooks/exhaustive-deps
 
     const cli = useContext(MatrixClientContext);
-    const onClientSync = useCallback((syncState, prevState) => {
+    const onClientSync = useCallback((syncState: SyncState, prevState: SyncState | null) => {
         // Consider the client reconnected if there is no error with syncing.
         // This means the state could be RECONNECTING, SYNCING, PREPARED or CATCHUP.
         const reconnected = syncState !== "ERROR" && prevState !== syncState;
diff --git a/src/components/views/dialogs/spotlight/Option.tsx b/src/components/views/dialogs/spotlight/Option.tsx
index c7d504aa0b4..d15b781fcff 100644
--- a/src/components/views/dialogs/spotlight/Option.tsx
+++ b/src/components/views/dialogs/spotlight/Option.tsx
@@ -26,6 +26,7 @@ interface OptionProps {
     id?: string;
     className?: string;
     onClick: ((ev: ButtonEvent) => void) | null;
+    children?: ReactNode;
 }
 
 export const Option: React.FC<OptionProps> = ({ inputRef, children, endAdornment, className, ...props }) => {
diff --git a/src/components/views/directory/NetworkDropdown.tsx b/src/components/views/directory/NetworkDropdown.tsx
index 8736e974e83..deb92858538 100644
--- a/src/components/views/directory/NetworkDropdown.tsx
+++ b/src/components/views/directory/NetworkDropdown.tsx
@@ -26,7 +26,11 @@ import SdkConfig from "../../../SdkConfig";
 import { SettingLevel } from "../../../settings/SettingLevel";
 import SettingsStore from "../../../settings/SettingsStore";
 import { Protocols } from "../../../utils/DirectoryUtils";
-import { GenericDropdownMenu, GenericDropdownMenuItem } from "../../structures/GenericDropdownMenu";
+import {
+    AdditionalOptionsProps,
+    GenericDropdownMenu,
+    GenericDropdownMenuItem,
+} from "../../structures/GenericDropdownMenu";
 import TextInputDialog from "../dialogs/TextInputDialog";
 import AccessibleButton from "../elements/AccessibleButton";
 import withValidation from "../elements/Validation";
@@ -181,7 +185,7 @@ export const NetworkDropdown: React.FC<IProps> = ({ protocols, config, setConfig
     }));
 
     const addNewServer = useCallback(
-        ({ closeMenu }) => (
+        ({ closeMenu }: AdditionalOptionsProps) => (
             <>
                 <span className="mx_GenericDropdownMenu_divider" />
                 <MenuItemRadio
diff --git a/src/components/views/elements/PersistentApp.tsx b/src/components/views/elements/PersistentApp.tsx
index dfed54a3ba0..0e876d9a37a 100644
--- a/src/components/views/elements/PersistentApp.tsx
+++ b/src/components/views/elements/PersistentApp.tsx
@@ -15,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { ContextType, CSSProperties, MutableRefObject } from "react";
+import React, { ContextType, CSSProperties, MutableRefObject, ReactNode } from "react";
 import { Room } from "matrix-js-sdk/src/matrix";
 
 import WidgetUtils from "../../../utils/WidgetUtils";
@@ -28,6 +28,7 @@ interface IProps {
     persistentRoomId: string;
     pointerEvents?: CSSProperties["pointerEvents"];
     movePersistedElement: MutableRefObject<(() => void) | undefined>;
+    children?: ReactNode;
 }
 
 export default class PersistentApp extends React.Component<IProps> {
diff --git a/src/components/views/messages/RoomPredecessorTile.tsx b/src/components/views/messages/RoomPredecessorTile.tsx
index 3166373fe04..36679d906d6 100644
--- a/src/components/views/messages/RoomPredecessorTile.tsx
+++ b/src/components/views/messages/RoomPredecessorTile.tsx
@@ -17,7 +17,7 @@ limitations under the License.
 
 import React, { useCallback, useContext } from "react";
 import { logger } from "matrix-js-sdk/src/logger";
-import { MatrixEvent, Room } from "matrix-js-sdk/src/matrix";
+import { MatrixEvent, Room, RoomState } from "matrix-js-sdk/src/matrix";
 
 import dis from "../../../dispatcher/dispatcher";
 import { Action } from "../../../dispatcher/actions";
@@ -52,7 +52,7 @@ export const RoomPredecessorTile: React.FC<IProps> = ({ mxEvent, timestamp }) =>
     const predecessor = useRoomState(
         roomContext.room,
         useCallback(
-            (state) => state.findPredecessor(msc3946ProcessDynamicPredecessor),
+            (state: RoomState) => state.findPredecessor(msc3946ProcessDynamicPredecessor),
             [msc3946ProcessDynamicPredecessor],
         ),
     );
@@ -63,9 +63,9 @@ export const RoomPredecessorTile: React.FC<IProps> = ({ mxEvent, timestamp }) =>
 
             dis.dispatch<ViewRoomPayload>({
                 action: Action.ViewRoom,
-                event_id: predecessor.eventId,
+                event_id: predecessor?.eventId,
                 highlighted: true,
-                room_id: predecessor.roomId,
+                room_id: predecessor?.roomId,
                 metricsTrigger: "Predecessor",
                 metricsViaKeyboard: e.type !== "click",
             });
@@ -126,7 +126,7 @@ export const RoomPredecessorTile: React.FC<IProps> = ({ mxEvent, timestamp }) =>
 
     const predecessorPermalink = prevRoom
         ? createLinkWithRoom(prevRoom, predecessor.roomId, predecessor.eventId)
-        : createLinkWithoutRoom(predecessor.roomId, predecessor.viaServers, predecessor.eventId);
+        : createLinkWithoutRoom(predecessor.roomId, predecessor?.viaServers ?? [], predecessor.eventId);
 
     const link = (
         <a href={predecessorPermalink} onClick={onLinkClicked}>
diff --git a/src/components/views/messages/TextualEvent.tsx b/src/components/views/messages/TextualEvent.tsx
index ae94fd31f9e..35351ce531c 100644
--- a/src/components/views/messages/TextualEvent.tsx
+++ b/src/components/views/messages/TextualEvent.tsx
@@ -27,6 +27,7 @@ interface IProps {
 
 export default class TextualEvent extends React.Component<IProps> {
     public static contextType = RoomContext;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public render(): React.ReactNode {
         const text = TextForEvent.textForEvent(
diff --git a/src/components/views/messages/TimelineSeparator.tsx b/src/components/views/messages/TimelineSeparator.tsx
index 78e0d1fd655..b3a2b9ccfb0 100644
--- a/src/components/views/messages/TimelineSeparator.tsx
+++ b/src/components/views/messages/TimelineSeparator.tsx
@@ -14,10 +14,11 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React from "react";
+import React, { ReactNode } from "react";
 
 interface Props {
     label: string;
+    children?: ReactNode;
 }
 
 export const enum SeparatorKind {
diff --git a/src/components/views/pips/WidgetPip.tsx b/src/components/views/pips/WidgetPip.tsx
index 9bba2ccc534..a1710d16ccc 100644
--- a/src/components/views/pips/WidgetPip.tsx
+++ b/src/components/views/pips/WidgetPip.tsx
@@ -34,6 +34,7 @@ import { WidgetType } from "../../../widgets/WidgetType";
 import { WidgetMessagingStore } from "../../../stores/widgets/WidgetMessagingStore";
 import WidgetUtils from "../../../utils/WidgetUtils";
 import { ElementWidgetActions } from "../../../stores/widgets/ElementWidgetActions";
+import { ButtonEvent } from "../elements/AccessibleButton";
 
 interface Props {
     widgetId: string;
@@ -62,7 +63,7 @@ export const WidgetPip: FC<Props> = ({ widgetId, room, viewingRoom, onStartMovin
     const call = useCallForWidget(widgetId, room.roomId);
 
     const onBackClick = useCallback(
-        (ev) => {
+        (ev: ButtonEvent) => {
             ev.preventDefault();
             ev.stopPropagation();
 
@@ -87,7 +88,7 @@ export const WidgetPip: FC<Props> = ({ widgetId, room, viewingRoom, onStartMovin
     );
 
     const onLeaveClick = useCallback(
-        (ev) => {
+        (ev: ButtonEvent) => {
             ev.preventDefault();
             ev.stopPropagation();
 
diff --git a/src/components/views/right_panel/UserInfo.tsx b/src/components/views/right_panel/UserInfo.tsx
index 6f8fd9790b0..159bc9dbf12 100644
--- a/src/components/views/right_panel/UserInfo.tsx
+++ b/src/components/views/right_panel/UserInfo.tsx
@@ -424,6 +424,7 @@ export const UserOptionsSection: React.FC<{
     member: Member;
     canInvite: boolean;
     isSpace?: boolean;
+    children?: ReactNode;
 }> = ({ member, canInvite, isSpace, children }) => {
     const cli = useContext(MatrixClientContext);
 
@@ -1036,7 +1037,7 @@ const IgnoreToggleButton: React.FC<{
     }, [cli, member.userId]);
     // Recheck also if we receive new accountData m.ignored_user_list
     const accountDataHandler = useCallback(
-        (ev) => {
+        (ev: MatrixEvent) => {
             if (ev.getType() === "m.ignored_user_list") {
                 setIsIgnored(cli.isUserIgnored(member.userId));
             }
diff --git a/src/components/views/rooms/RoomHeader.tsx b/src/components/views/rooms/RoomHeader.tsx
index 9cf63e474d6..11873ee129e 100644
--- a/src/components/views/rooms/RoomHeader.tsx
+++ b/src/components/views/rooms/RoomHeader.tsx
@@ -116,7 +116,10 @@ export default function RoomHeader({
 
     const askToJoinEnabled = useFeatureEnabled("feature_ask_to_join");
 
-    const videoClick = useCallback((ev) => videoCallClick(ev, callOptions[0]), [callOptions, videoCallClick]);
+    const videoClick = useCallback(
+        (ev: React.MouseEvent) => videoCallClick(ev, callOptions[0]),
+        [callOptions, videoCallClick],
+    );
 
     const toggleCallButton = (
         <Tooltip label={isViewingCall ? _t("voip|minimise_call") : _t("voip|maximise_call")}>
diff --git a/src/components/views/settings/UserProfileSettings.tsx b/src/components/views/settings/UserProfileSettings.tsx
index a104aabb1d7..b793f27dd64 100644
--- a/src/components/views/settings/UserProfileSettings.tsx
+++ b/src/components/views/settings/UserProfileSettings.tsx
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { ChangeEvent, useCallback, useEffect, useMemo, useState } from "react";
+import React, { ChangeEvent, ReactNode, useCallback, useEffect, useMemo, useState } from "react";
 import { logger } from "matrix-js-sdk/src/logger";
 import { EditInPlace, Alert, ErrorMessage } from "@vector-im/compound-web";
 import { Icon as PopOutIcon } from "@vector-im/compound-design-tokens/icons/pop-out.svg";
@@ -37,7 +37,7 @@ import Modal from "../../../Modal";
 import defaultDispatcher from "../../../dispatcher/dispatcher";
 import { Flex } from "../../utils/Flex";
 
-const SpinnerToast: React.FC = ({ children }) => (
+const SpinnerToast: React.FC<{ children?: ReactNode }> = ({ children }) => (
     <>
         <InlineSpinner />
         {children}
diff --git a/src/components/views/spaces/QuickSettingsButton.tsx b/src/components/views/spaces/QuickSettingsButton.tsx
index cf031e4ff16..a118a13bbc3 100644
--- a/src/components/views/spaces/QuickSettingsButton.tsx
+++ b/src/components/views/spaces/QuickSettingsButton.tsx
@@ -45,7 +45,7 @@ const QuickSettingsButton: React.FC<{
         useSettingValue<Record<MetaSpace, boolean>>("Spaces.enabledMetaSpaces");
 
     const currentRoomId = SdkContextClass.instance.roomViewStore.getRoomId();
-    const developerModeEnabled = useSettingValue("developerMode");
+    const developerModeEnabled = useSettingValue<boolean>("developerMode");
 
     let contextMenu: JSX.Element | undefined;
     if (menuDisplayed && handle.current) {
diff --git a/src/hooks/useAccountData.ts b/src/hooks/useAccountData.ts
index d59910d5033..ad25f61465e 100644
--- a/src/hooks/useAccountData.ts
+++ b/src/hooks/useAccountData.ts
@@ -26,9 +26,9 @@ export const useAccountData = <T extends {}>(cli: MatrixClient, eventType: strin
     const [value, setValue] = useState<T | undefined>(() => tryGetContent<T>(cli.getAccountData(eventType)));
 
     const handler = useCallback(
-        (event) => {
+        (event: MatrixEvent) => {
             if (event.getType() !== eventType) return;
-            setValue(event.getContent());
+            setValue(event.getContent<T>());
         },
         [eventType],
     );
diff --git a/src/languageHandler.tsx b/src/languageHandler.tsx
index 0a80be89f48..27a886ddf98 100644
--- a/src/languageHandler.tsx
+++ b/src/languageHandler.tsx
@@ -53,7 +53,7 @@ const FALLBACK_LOCALE = "en";
 counterpart.setFallbackLocale(FALLBACK_LOCALE);
 
 export interface ErrorOptions {
-    // Because we're mixing the subsitution variables and `cause` into the same object
+    // Because we're mixing the substitution variables and `cause` into the same object
     // below, we want them to always explicitly say whether there is an underlying error
     // or not to avoid typos of "cause" slipping through unnoticed.
     cause: unknown | undefined;
@@ -78,16 +78,15 @@ export interface ErrorOptions {
 export class UserFriendlyError extends Error {
     public readonly translatedMessage: string;
 
-    public constructor(message: TranslationKey, substitutionVariablesAndCause?: IVariables & ErrorOptions) {
-        const errorOptions = {
-            cause: substitutionVariablesAndCause?.cause,
-        };
+    public constructor(
+        message: TranslationKey,
+        substitutionVariablesAndCause?: Omit<IVariables, keyof ErrorOptions> | ErrorOptions,
+    ) {
         // Prevent "Could not find /%\(cause\)s/g in x" logs to the console by removing it from the list
-        const substitutionVariables = { ...substitutionVariablesAndCause };
-        delete substitutionVariables["cause"];
+        const { cause, ...substitutionVariables } = substitutionVariablesAndCause ?? {};
+        const errorOptions = { cause };
 
-        // Create the error with the English version of the message that we want to show
-        // up in the logs
+        // Create the error with the English version of the message that we want to show up in the logs
         const englishTranslatedMessage = _t(message, { ...substitutionVariables, locale: "en" });
         super(englishTranslatedMessage, errorOptions);