> I've heard that - what is your experience? Downvotes and exclusion? Are there more 'open' servers?

Fediverse has plenty of servers which are "free speech" adjacent, which most Mastodon servers close off since its easier for them to police what their users can see than let them do it themselves. The vast majority of them do not run the Mastodon software, and feel far more "wild west" with all the shitposters. But if you want to talk with actual hackers and are into that sort of thing, it's fun times.