The fediverse (network of activitypub servers, including mastodon) itself doesn't censor anything at all, but if you don't moderate your instance then other instances might decide to stop federating with you to protect their users.
As far as I understood, they're not doing that on a case-by-case basis, but are using centralized block-lists (which every admin can choose to follow automatically). That's a step up from raw centralized censorship, but it's not a big step.
Most admins AFAIK don't have centralized blocklists but when the new bad instances pop up there tend to be #fediblock posts pretty fast, and they get shared pretty widely.
The only thing these networks censor is anything that is illegal in their hosted jurisdiction
Truth Social has apparently banned (and shadow banned) lots of people for posting anti-Trump and anti-GOP political messages.
The only thing these networks censor is anything that is illegal in their hosted jurisdiction i.e the US.