You can have a poke around at !fediverse@lemmy.world but actual stats seem elusive, although I didn't try hard, in server search is bad (although Kagi now does it, might have better luck there).

I found this about 200K lemmy.world users, and in it was a graph from fedidb.com, which is 3 weeks later 'server error', but indicates MAU are much lower, 14.5K a year ago and 12.5k recently. That's just one (large) server, might mean diaspora which would be good, but seems to indicate stable-ish with slow decline.

I am sanguine, quite like the types that have washed up on this shore, good enough for this person to use.