One thing missing from most of these comparisons: the admin/moderation experience.
Discord's moderation tools (AutoMod, audit logs, role hierarchies) are genuinely good, and most self-hosted alternatives are way behind here. If you're running a community server, this matters a lot.
My ranking for communities (not just friend groups):
- Matrix (Synapse/Conduit) — best moderation tools of the self-hosted options, rooms/spaces model works well
- Revolt — closest Discord clone, but moderation is still basic
- Mumble/TeamSpeak — voice-only, but rock solid for gaming guilds that don't need text
For just friends? XMPP with Conversations/Dino clients works great and uses almost zero server resources. I run an ejabberd instance on a $5 VPS alongside 5 other services.