What can Lemmy federate with?

Mastodon for sure, you can even use mastodon bots from lemmy, and there will be limited compatibilty witth anything else using activity pub.

So apparently Peertube works well, in part because the structure of the two platforms map onto each other well. Communities -> Posts -> Comments = Channels -> Videos -> Comments.

I experimented once, and from memory you can definitely subscribe to a peertube channel here. But I don't know my way around peertube so I don't know how well it works.

In theory, it should work with all of them, but in practice it's messy and clunky as all of them use ActivityPub in subtly different ways, with their own extensions and quirks.

Also Lemmy versions pre 0.18 (i want to say, unsure) won't work with GoToSocial or Mastodon instances with secure mode enabled. The recent versions should though.

What can Lemmy federate with?

Yes.

There's also Diaspora, and I don't know if Lemmy can federate with that.

I have summarized here what I have found out so far, but is currently only available in German https://handbuch.rollenspiel.monster/lemmy/communication/

I've noticed that Lemmy has a hard time federating to non-Lemmy instances. Looking up a user/community on Calckey/Mastodon shows a lot of posts and random things missing.

@trymeout Hello from Mastodon!