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
They said they were open to it but they had zero priority of doing it themselves, and essentially “submit a PR if you want it”. A shame really, their interface is great, and such an easy setup. If they implemented either xmpp or matrix I would switch immediately. All of my friends want a discord clone that “just” works, but no one wants to go to this server for this group and then login to that server for that group. They want a single-pane interface like what discord offers.
Shortsighted to not implement that IMO.