Urbit? Yea. And even more interesting is

Groundwire

Install Groundwire

Groundwire is a Bitcoin computing stack built on Urbit. A personal server with a built-in SPV wallet, Nostr client, and MCP server for AI agents. I...

- they're re-doing the identity layer using Bitcoin, and are working on a nostr client. I tried it and it's all a little buggy so far, but I know there are good people working on it. ...All that said, I'm pretty exhausted by urbit at this point. I have very little patience for it and it's history of baggage and stupid ideas.