Is it any service that includes the ability to federate? If so, are Matrix/XMPP/other non-ActivityPub services part of the Fediverse, or does Fediverse really just mean ActivityPub?
The context is wanting to promote a Matrix chat room on discuss.online: #online.discuss:discuss.online (see post). Does it belong in Lemmy communities like this one, !fedigrow@lemm.ee, etc? Or does it not count as part of the Fediverse?
It’s federated, just not to the ActivityPub universe, right? People have been able to join rooms on discuss.online using their matrix.org accounts, which to me counts as federated.
Matrix servers can talk to each other, so yes, they are federated. But Matrix is not ActivityPub.