Well there's also techies who don't (only) use Linux and like (some) sports. More of a Sci-Fi and Comic Book guy than anime here.

Let's see how this grows.

Mastodon has the same fatal flaw. They want to keep your history and relationships hostage so you can’t leave.

You can migrate your relationships to a new Mastodon server.

And while you can't directly transfer the history (the debate over how/whether to do this has gone on for literally years), you can export an archive you can keep locally, and there are tools out there to parse it and convert it to some other form (static website, whatever). Someone's probably written an importer by now, though I'd have to look.

Future instance owners and moderators don’t want users and communities to be able to migrate seamlessly. Mastodon has the same fatal flaw

This is misrepresentative for a few ways.

For one, you can in fact migrate your mastadon account, fairly easily in fact.

For another thing, instance owners and moderators don't really get to choose whether migration is possible, the code contributors do. I suppose instance owners could start forking their own version of lemmy to make that harder, but ultimately there will always be folks willing to host the "best" version, and so people will just leave