There is a saying: “facts have a liberal bias”. :-) Some people ofc vehemently disagree.

Each instance is different, as is each community. Many do not follow their own rules, especially about “no politics allowed” but it creeps in everywhere. Tbf, modding is a hard job.

Though you can block communities that you don’t want to see in your feed, and even entire instances (it won’t stop people from them downvoting you or even commenting on your stuff, but it will stop notifications being sent to you when they do. Get to it via Settings -> Blocks -> Instance. Users and communities can be done similarly but it’s easier to just visit their page and hit the block button there. There’s a saying about that too: block early and often, for the sake of your sanity.

I don’t know about instances - there’s a lot to look at like lemm.ee, lemmy.cafe, reddthat.com, sh.itjust.works, etc. - but I hope this helped in other ways:-).