Number of (active) Lemmy users seems to stabilize and I think this is a great thing. Indeed we got a lot of users when reddit shutdown its API (I was among them despite being a long time oss user), many have left, but the community seems now to stabilize to ~ ½ of the big grow in june '23. I think this is very nice for lemmy, we can be proud of this project.
The stats come from: https://fedidb.org/software/lemmy
Yep, there must be lots of uncounted lurkers. If you look at the active user charts at The Federation there was a spike in December when 0.19.0 released. I expect we'll see more spikes as additional instances upgrade to 0.19.
https://the-federation.info/platform/73