IIUC Mastodon is a twitter alternative; https://diasporafoundation.org/ is more targeted at replacing FB.

Diaspora has been around for a while; I remember joining about 6-7 years ago, but it suffered from the problem all new social networking sites suffer from -- nobody I knew or wanted to follow was there, so I abandoned it.

I've since come to the conclusion that I'm not really a social networking type of person.

Both Mastodon and Diaspora suffer from absolutely horrible names.

If you don't like the UI there is Pleroma ( https://pleroma.social/ ) which is compatible with the Fediverse so you can interact with Mastodon instances.