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
There’s a wide gap of stuff one can do between IRC and “chat with voice channels”. For example, having a better protocol with better formatting options, a moderation API, better account management, other forms of multimedia (page embeds, images).