By which I mean in terms of usage, development, or stability. Also along those lines, which English-speaking instances would you recommend?
Interested as Misskey & forks have some feature edges over Mastodon in my opinion, but it’s somewhat harder to find discussion/info about them.
I used to use Calckey but it soon morphed into Firefish, which also didn’t last long. So, as far as stability goes: Misskey may be stable, its forks not so much. I’m currently using Catodon (catodon.social) and the only functionality missing is the antennas.
On the other hand, most of the firefish crowd migrated to Iceshrimp. You can check out the Fediverse Observer to find some english-speaking instances.
Firefish > Iceshrimp
Hilarious, makes me kind of want to see it fail again just to see what people come up with as the next name in line.