Hi @npub1sq24...gk0y I just a FYI on 
a federation protocol "heavily inspired by ActivityPub" which I just bumped into via @Erlend Sogge Heggen .. didn't have a deep look yet, but thought it might be interesting given your own musings re:FeatherPub.
Versia Documentation
Introduction to the Versia Protocol, a communication medium for federated applications, using the HTTP stack.