Most are in beta here are some I found

Liftoff! https://testflight.apple.com/join/e6ZEbxuR

Edit new test flight link: https://testflight.apple.com/join/jKENkGjX

Thunder https://testflight.apple.com/join/9n8xrqvH

Memmy https://testflight.apple.com/join/6jaRU6rD

Mlem https://testflight.apple.com/join/MelFP11Y

Wefwef PWA (Basically an apollo clone) https://wefwef.app

Lemmy PWA (not really an app installable via iOS share menu)