More of a small diaspora sort of situation I think, at least relative to the amount of people that use Reddit.

As to where besides Lemmy/Kbin, there’s some mentions across similar discussions of going to Tildes, Squabbles.io, Raddle, Discord, and I’d suspect a tiny minority may have gone back to plain old forums and some may be working on setting some up (e.g. Jellyfin’s devs went ahead & did so). If I were to guess without hard numbers, I would guess that the majority that made any move may have simply gone to Discord, with another large amount giving Lemmy/Kbin a go, and a smaller amount of folks going to the others mentioned (i.e. Tildes/Squabbles/Raddle/other forums or trying to set up forums).