Alternatives

Theres also misskey, calckey, and plemora

I haven't looked at peer tube yet but I highly recommend anyone who is curious about a federated Twitter check out Mastadon.

It feels like a much more polished experience than Lemmy and I think is a good example of what federated sites can become.

Also it wasn't in the question, but Pixelfed is basically a federated version of Instagram for those curious as well.