907
Bluesky now has 30 million users.
(www.theverge.com)
This is a most excellent place for technology news and articles.
Roughly 10 million.
I would consider 1/3 a notable contender. Granted, only ~1 million of those users are active daily, but that's still very significant for a FOSS alternative.
EDIT: Source
Those numbers are small in the grand scheme of things, but for a newer and open source community developed project those are absurd numbers, ESPECIALLY because it isn't a flash in the pan, many of those users call the fediverse home and use it daily.