From https://fediverse.observer/stats
Which seems to not at all come close to representing what you might actually see on Lemmy, not that Lemmy is tiny either.
Has there been any attempt to measure the total active Lemmy userbase? This would depend on the definition of Active but any working definition would be more useful than counting account creation. Something like “posted at least once this quarter”.
That is for the fediverse overall. Most of that comes from Mastodon. I personally have a little more faith in fedidb.org and their numbers. Also, worth noting the criteria for active users on Lemmy was recently changed to include votes, whereas before it only counted comments and posts.