I see very few people use "toot" much on Mastodon now, though. It's certainly in use, but "post" seems to be more common, in part I think because it saves is from switching back and forth when talking about Twitter, but also because Mastodon is just one of many applications in the Fediverse. A number of my followers are on Pleroma or Misskey, for example, and a "toot" doesn't have the same connection to their software.