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
They are (mostly) federated, which means that users from one can see what's on the others. There are a few exceptions to this, primarily for extremist content which are not federated with most of the other servers.