nostr:npub1h0uj825jgcr9lzxyp37ehasuenq070707pj63je07n8mkcsg3u0qnsrwx8 is as close as it gets right now. nostr:npub1exv22uulqnmlluszc4yk92jhs2e5ajcs6mu3t00a6avzjcalj9csm7d828 good too, but not nostr per se.

NIP-104 is coming in hot, which provides a protocol -level implementation spec based on MLS (Signal-grade messaging scaled to groups).

Clients will start implementing over the next few months I guess.