If you're looking for a social protocol that is even more decentralized than federated sites like Mastodon, have a look at Nostr. Every user account is just a public/private key pair. When you create a post, you sign it with you private key and the post is stored on a relay server. Anyone can run a relay server.

I find Nostr much more exciting than federated sites, b/c it uses decentralized ids. You never have to worry about losing your social graph due to a federated server admin shutting down their server or banning you.

https://github.com/nostr-protocol/nostr