@eniko

fediverse.observer and fedidb.com both have stats covering the Fediverse. Values don't necessarily agree due to different filtering and processing, but on first approximation they're pretty close and probably as good a measure as one can get.

That being said, Mastodon still remains the most widely adopted platform, so the numbers aren't that much different if one limits themselves to it (the next platform up was something like 1:10 last time I checked).