Stoat (formerly known as Revolt) is a selfhostable, FOSS replacement for discord [Group chats and voice channels you can join any time].
Cool new name, however not as easy to use in other languages.
Voice chat is stil not officialy implemented.
Self-hosting there. Apparently nothing to do for you if you had already hosted before the name change.
The Android app has unfortunately disappeared (not been updated) on F-droid.
Edit: added short description for clarification
This Movim thing is giving me really good vibes! No AI in sight, nor crypto shit. Thanks so much for the suggestion! Why don’t I hear anyone talking about it? If you have any other smaller open source projects to suggest, please let me know lol