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
Compared to some other alternatives, I think the thing it really has going for it is how simple it is. It’s really a drop in replacement for discord, something I actually think maybe my friends that don’t really care about Foss would consider switching to. They’ve told me they don’t want to take the time to learn a new messaging software, I don’t think they’d have to with this.