If you don't mind writing the UI native, sharing only business logic code, Kotlin is an option: https://kotlinlang.org/docs/multiplatform.html#kotlin-multip...
Kotlin also can do the UI if you use Compose: https://www.jetbrains.com/lp/compose-multiplatform/ ... however, iOS support is still in alpha, and Web is "experimental". If you're not willing to cope with that (expect to have to change your code as they develop the framework) then Flutter is the way as it's pretty stable already on all platforms.
If you already know Typescript and React, you may also consider React Native (but I can't attest to its performance on iOS or anywhere else): https://reactnative.dev/