Next to Mastodon.world and Lemmy.world I am also running Calckey.world.
This was running Calckey, a Misskey fork. That was re-branded to FireFish (that's the danger of running sites with the software name in the URL... :-) ).
Unfortunately due to circumstances the FireFish software will no longer be maintained. Therefore I was looking for another Misskey fork that could replace it, and I found Sharkey.
This looks really nice.
So being who I am, I registered https://sharkey.world and installed it. It still needs some configuring and branding, but it works and you can use it! (As you will see it currently uses the Calckey.world branding)
I will write a brief how-to on migrating from Calckey to Sharkey and hope the calckey.world users will migrate.