Not 100%, if people's own self reports are to be believed (on Reddit, Bluesky, X, etc.). For example this post made a couple years after the Rexodus: https://www.reddit.com/r/RedditAlternatives/comments/1jqvq6k/looking_for_reddit_alts_that_are_not_lemmy/.

Also, I found this older post and its comments quite interesting: https://www.reddit.com/r/RedditAlternatives/comments/170ie8t/regarding_the_recent_complaints_about_lemmy_being/.