This is indeed excellent and they are currently working hard on making it a nice alternative to Discord.

Our Lemmy instance has been running it as a supplementary service for quite some time now and it is relatively popular with our members: https://movim.slrpnk.net/

Oh man, seeing folks suggest it as a Discord alternative always had me uninterested, because I don’t even use Discord and it just seemed like yet-another-standard.
Now I’m reading this really technical title for a talk which mentions XMPP and I’m instantly sold.

Well, to be honest, “Movim” also sounded like a VC-funded startup. Looks like it’s a bus-factor-of-1 open-source project instead, which I have significantly more trust in.