That's kind of the thing about the fediverse: that's basically not possible. Any instance that doesn't engage in some blocking will probably be blocked for what it doesn't block. You could, of course, run your own instance, but obviously that's its own can of worms.

So... It's tricky.

edit: also, sites like joinmastodon USUALLY just completely exclude anything too controversial, for pretty obvious reasons. Dunno about join-lemmy but I'd bet on it.