Thunder is an open Lemmy app for iOS and Android that is currently under development. You won’t find it in any app store, so it’s not as well known as Jerboa. Still, it’s an excellent app.
The client is written in Flutter/Dart. If you have any development skills, lend a hand!
Just going to add it does look like its available on android through izzyondroid fdroid repo. I’m not a developer and I wanted toupdates automatically as they are released so this is great.