[freax4evar]

There's diaspora [0] and GNU social [1], but those haven't yet managed to pop up into the mainstream. Network effects should ensure that they do not anytime soon. With that said, the mounting controversy over Facebook and Twitter's moderation may end up pushing marginalized groups into these platforms.

[0]: https://diasporafoundation.org/

[1]: https://www.gnu.org/software/social/

[zyxley]

Both of these are doomed in the mainstream until you can "just join" instead of having to pick from a list of servers you know nothing about anyway.