If you check the example in the documentation and modify its useEffect to:

  useEffect(() => {
    const subscription = AppState.addEventListener("change", nextAppState => {
      if (
        appState.current.match(/inactive|background/) &&
        nextAppState === "active"
      ) {
        console.log("App has come to the foreground!");
      }

      appState.current = nextAppState;
      setAppStateVisible(appState.current);
      console.log("AppState", appState.current);
    });

    console.log(typeof subscription.remove);  // <--- ERROR!

    return () => {
      subscription.remove();
    };
  }, []);

(test this snack)

you can see .remove() is not a property of void (as expected). Also, after upgrading to the last react native version (0.68.2), I am getting the warning

EventEmitter.removeListener('appStateDidChange', ...): Method has been deprecated. Please instead use remove() on the subscription returned by EventEmitter.addListener.

while removeEventListener is not marked as @deprecated in the core, and addEventListener returns void.

export interface AppStateStatic {
    currentState: AppStateStatus;

    /**
     * Add a handler to AppState changes by listening to the change event
     * type and providing the handler
     */
    addEventListener(type: AppStateEvent, listener: (state: AppStateStatus) => void): void;

    /**
     * Remove a handler by passing the change event type and the handler
     */
    removeEventListener(type: AppStateEvent, listener: (state: AppStateStatus) => void): void;
}

Am I missing something?

Also see: https://github.com/facebook/react-native/issues/33151