For me personally, Jerboa is the best Android Lemmy app that I've tried, and I have tried several of them. I'll just be glad when Sync for Lemmy is released.
Have you tried just signing in to the instance. I know when I applied to join one of the instances, I never received an email telling me that my application had been accepted. So after a couple days, I just tried signing in, and it worked.
Yeah, it's been almost unusable for me as well. I'm currently using my account that I have on another instance. Hopefully though, things will get better on lemmy.world.