It seems that any Lemmy.world and Lemmy.ml hosted communities aren’t any longer federating properly via kbin as I started getting 404 errors on all of them. Examples:
https://lemmy.world/c/personalfinance: ok
https://kbin.social/m/[email protected]: 404
https://lemmy.ml/c/fire: ok
https://kbin.social/m/[email protected]: 404
https://beehaw.org/c/finance: ok
https://kbin.social/m/[email protected]: ok
@Alexmitter Thanks for linking the relevant repo issue, that explains it.