As far as I can tell from my venture into Mastodon’s feeds, the demographics of that part of Fediverse isn’t that different from what Lemmy has: the same political takes, FOSS stuff, “big corpos bad”, etc.
I wonder, is there anything that Mastodon excels at that Lemmy just doesn’t provide? For example, I noticed that there are game developers and artists posting their stuff on Mastodon. Not many game developers (or any creatives, really) on Lemmy though.
@catfeeder mastodon has a much larger community, so people that find their way through contribute here. It’s a one-way street though. You can’t contribute to mastodon from you threadiverse account (mbin/kbin community so small that it’s not worth the mention).