I think it’s possible to host a lemmy instance over TOR, though I’m not sure if you could federate with clear net instances over Tor. There is also Lemmy Lite, which is a JS-less interface for lemmy instances. Their repo is a bit stale but in theory it should still work with modern versions of lemmy.

You can setup an instance and see how well it works. Of course js is required for now (but you could use a mobile/desktop Lemmy app over Tor). For federation it would probably be necessary that peer instances also have Tor installed, to resolve .onion Urls. Or use a clearnet domain for federation.