Hubzilla
A federated platform (Mike Macgirvin) known for "nomadic identity" — your identity isn't locked to a single server. Via the Zot protocol you can clone your account across several servers so you survive a server shutting down, seamlessly.
Unique feature: nomadic identity solves a Fediverse Achilles' heel — on Mastodon your account dies if the instance disappears; on Hubzilla you have copies on several "hubs" and can move without losing followers or content. It builds on Zot/Zot6 (its own protocol) but can also speak ActivityPub. More than a microblog: channels, wiki, file storage, calendar, web pages — a whole "decentralized web platform". Trade-off: powerful but complex and hard for beginners; a smaller community than Mastodon. Part of Macgirvin's long line of projects (Friendica → Hubzilla → (streams)). A pioneer of account-portability ideas that Bluesky later addressed in its own way.