Fedi Facebook alternative. Never felt any need to look into it

It was one of the original attempts at federated social media. With a more Facebook feel. There was a Frendica, Identica, Diaspora. Frendica (well Mistpark as it was called back then) was the first to implement other protocols, connecting to the other platforms.

Pump.io was really the first to implement ActivityPub to my knowledge.

I’ve been hanging around these spaces a long time.

It's more of a Facebook alternative. It has almost all the bells and whistles of it, minus the ones that imply constant surveillance of the users (shadow profiles for instance) - you have a calendar where you can add events, or you can see the events you joined, you have a permission system on your posts, replies are seen as part of a post instead of being individualized, you have an activity log, etc.