The Funkwhale for Android app is a nice alternative to Ultrasonic, but so far the experience is not as smooth as Ultrasonic.
Main issues I've been facing are:
- scrambled / deteriorated sound sometime when listening through the App (less so lately)
- the app often loses access / renders empty listing, requiring a logout and new login to access my Funkwhale account again
Those issues seem to have been partially addressed, but as of today, using the dev version from F-Droid, I am still facing. I'll update this thread as things go. For now I recommend to use Ultrasonic.
For info, there is a Matrix room for the Funkwhale Android app: #funkwhale-android:matrix.org