Liftoff recognizes more than just lemmy.world.

Go to the bottom right into profile. Upper right in the profile screen you'll see a settings gear icon. Tap that, then select accounts.

From there, it should be pretty obvious. But, yeah, it would be nice if liftoff had a front facing accounts section like most of the others do. Great app though!

If you still don't like it, connect and jerboa are currently the most reliable, with thunder being only a tad behind (but otherwise excellent) with tools g or, it was the last I checked yesterday, and I haven't seen an update for it).

But, all of those support multiple accounts.

Not that you need multiple accounts. You can access all of lemmy and kbin from a single account. You just have to search for the community within an instance, and it'll get pulled in if it isn't already. But you have to search the !community@instance, or http://instance/c/community format if it isn't already showing.

Community discovery can be a bit of a pain at times, but there's lemmyexplorer that serves as a good source until lemmy itself has more time to develop