Exploring multiple specs for group messaging within #Nostr: Can they coexist?
nostr:npub1zuuajd7u3sx8xu92yav9jwxpr839cs0kc3q6t56vd5u9q033xmhsk6c2uc gives a rundown of this, and the ongoing work to make it as interoperable and straightforward as possible for everyone, in BR081.