I only got on Bluesky a couple of months ago after a long wait, and honestly I don't think I've been on there once since setting up the account. A trickle of my Twitter contacts seemed to move over there in the early days but the trickle dried up and it doesn't look like many people are on there.
I hope it still finds a niche for itself, but the ridiculous invite rationing thing really does seem to have killed the momentum for them.
I've also lost interest in Mastodon, although again I'm willing to give it another go if it continues to grow. Mostly I've just found that I don't really need to replace Twitter in my life; I'm just fine without it...
ChromeOS is as much Linux as anything else is. It's controlled by a greedy megacorp, but so is Red Hat (IBM) or, idk, Oracle Linux. Yes it's based on an unusual immutable design, but immutable distros are now cropping up out of lots of projects (Fedora, SUSE, Ubuntu, amongst many others, not to mention the Steam Deck). It avoids using the GNU tool chain, but the alternatives that it uses are already used by other Linux distros (like Alpine). It now uses the standard Wayland graphics stack, and is in the process of moving from upstart (a previously widely used Linux init system) to systemd.
It's hard to come up with a definition of "Linux distro" that excludes ChromeOS without excluding a bunch of unambiguously Linux distros too.