fandom.ink is the instance that i've seen the most "my genre of fandom" on. i would probably just go there. there's also a kpop server. i think only the absolute tanking of twitter would lead to kpop fandom migrating there, if people have no choice. but otherwise, im not holding m breath! it's day 3 of my twitter deactivation and im finding it satisfying and tbh kind of a relief to primarily only be on discord.