Been reading some docs and felt like drawing to get a better picture.
Some things to note:
- Parenthesis indicate bridges
- Fed Bridgy and Mostr appear twice because I don't know if they allow cross-communication
- One-way arrows (→) indicate one-way communication, and two-ways arrows (⇄) indicate the two sides can talk with each other
- Threads to/from Facebook and Instagram communication appears with an interrogation mark because the information I could find didn't feel conclusive and I don't have an account to test myself
- Maybe I missed some bridges and protocols, but that'd be more of a lack of knowing; also intentionally ignored X/Twitter > Nitter > RSS > ActicityPub bridges because it felt too much of a stretch.
Cool. Looks about right to me, not that I'm an expert. Bridgy Fed and Mostr do allow you to chain them together and do Nostr <> AT communication (though more recently there's also Eclipse.Pub that does Nostr <> AT). There are also a few other protocols still in use (Diaspora, DFRN, Zot, Nomad - Diaspora, Friendica, Hubzilla, Streams respectively) although all but Diaspora all internally bridge to Activity Pub so I'm not sure how they'd fit into your model.
Didn't know Friendica and Hubzilla are other protocols. 👀