Matrix fits the bill. It's federated - you can have rooms and conversations across homservers seamlessly today. There are several implementations for both serve

Matrix fits the bill. It's federated - you can have rooms and conversations across homservers seamlessly today. There are several implementations for both server and client. It's still a way to go to be 100% though; for example portable identities - right now your user account is tied to a specific homeserver, yours or somebody elses. And first class tor (or i2p?) support with enough federation over either. Performance of synapse and elemnt, spoecifically, are also pretty poor. I really think it's on the right track though - all my reservations for matrix in its current state have been recognized by the maintainers and are on the roadmap.