I use all three: mastodon, bluesky, and twitter. Mostly because people I follow are on different platforms. Personally, I would settle for mastodon alone. There is a recent big wave of artists moving from twitter to bluesky because twitter got new policy that makes it impossible to opt-out from using images posted on twitter as AI training material. Actually those new rules to me sound like they’re problematic in terms of author rights in general, not only AI stuff.
“Universal” means that it’s unconditional. As I understand it, by design of the concept, everybody should receive it.