personally, i'm not in a hurry to find a discord alternative. instead, i'd prefer to find indie websites with chatrooms. my current favorites are
onio club and heck, our very own liquid crystal cafe

the downside of being in a website-specific chatroom is that you won't find the same people, and you'd have a hard time convincing your friends to join them (as is typical with telling friends to give up their social media addiction...) but the upside is that you get to make more friends and enjoy any website-specific quirks and trinkets. and who can argue against that?