The lingua franca options are effectively Xamarin, Flutter, and React Native. Xamarin's dev experience sucks and Flutter's perf isn't much different from React Native with a way less mature ecosystem.
There are people who should write platform-native mobile apps. For everybody else, React Native is fine. And, for my money, TypeScript is the most right programming language easily available on major platforms today, so that makes this one pretty self-evident to me.