The codeberg issue is kind of still an ugly scratch pad rn. The thing awaits a follow-up where stuff is more organized and easier to drill down into. Proper docs eventually.
A first step may be to name the discrete and granular building blocks that one should focus on when starting out on an #ActivityPub client-to-server adventure quest. Give them consistent names. And then to map all the various projects to that as a MDN-like who-supports-what table.