This is relevant to my interests because I don't want the hassle of running a rails app, but I sure would love to host enough of the endpoints to make my existing vps accept and transmit ActivityPub messages. Like a single-user server (which I fully recognize would remove any "Local Timeline" view but OTOH would mitigate having to switch servers/losing control of my fediverse identity

The ActivityPub spec itself seems pretty approachable, but a couple of alternative implementations I saw recently mention "Mastodon compatible" so I wonder how far it has deviated from the actual spec