Workaround for login to Android: Log in to the browser (on Android). In the settings / Social accounts generate a one-off login code. Use this code in the Android app to login. One remains logged on Android also after ending the app, so one does not have to repeat this procedure.

There is now an app available. The login process is, however, faulty. If I start the app on Android, I will be forwarded to the default browser (in my case Firefox). I log in there (via Twitter). You are then returned to the app, but you are still not logged in there.