I'm sure most Lemmy apps will add Kbin support down the line, too. The lead developer for Sync for Lemmy already said he's looking into it, I believe. At the moment, Kbin doesn't have an API though, so it's less straightforward to approach I guess.

For an app designed for Kbin first and Lemmy second, Artemis is under way and you can follow it here: https://kbin.social/m/ArtemisApp