Matrix is the ultimate alternative to Discord! It's a FOSS protocol, which has numerous server and client implementations available—much like the ActivityPub protocol.

divolt looks pretty good, has bridge support so you dont need to make all your friends move to something else

I heard about "guilded" but i don't have direct experience.

We could always go back to ventrilo servers for voice chats! I miss hopping into vent with my WoW guild for raids back in the day.