Honestly, despite not actually being federated, I've been using raw Git a lot recently. As opposed to ActivityPub, you can always download the current state lf the central repo and bring yourself up to current. I just wish it were easier to store binary data in it (e.g. sharing my MP3s between my laptop and phone)

Of course, that's not a collaborative use-case. I have no intention of opening my files to the world. Just noting that ActivityPub has some pretty severe limitations (if my mbin server is offline, I wont get the updates I missed while it was down, ever. And if I can't process messages in real-time, I miss those too).