I used to say “Welcome to Lemmy” to new joiners, but nowadays quite a few of them join Piefed instance, having a generic term is easier
You can’t follow Mastodon users from Lemmy or Piefed, using “Fedivers” seems too generic
Previous post on the same topic: https://lemmy.zip/post/33451610
And the word meta itself is used for meta communities on the Threadiverse which have nothing to do with Meta the company. Words existed before companies took them.