- 221 with over 5 accounts

- 74 with over 20 accounts

- 19 with over 250 accounts

- 8 with over 1000 accounts.

And only a handful of those have open signups (13 with open signups have >50 users).

Many of them are actually ActivityPub instances with a PDS bridge, e.g., https://join.wafrn.net/

And most of the other open signup instances are also primarily designed as their own social network, just using AT proto as a compatibility layer, e.g., https://sprk.so/ https://haruhwa.com/ (which is an invite-based, snapchat-style ephemeral social network), https://surf.social/, https://pckt.blog/ (a microblogging platform), aesthetic.computer (a collaborative programming/art platform)

That leaves only bluesky, blacksky, eurosky, selfhosted.social, self.surf and npmx.social.

Even during Facebook's heyday, the unsuccessful diaspora/friendica/gnu social/etc networks had more decentralization than that.