Mobile apps and games (Android and iOS) - Which programming language?

I learn Unity and C# in order to be making mobile apps and games for Android and iOS. But I don't know which programming language to choose for backend in games. I consider Kotlin, Dart and C# MAUI. Maybe you have other option. I don't want to learn Swift for iOS and Java for Android. I am only interested in cross platform solution - one language for back end.

AI in mobile games can I make in AI tools for Unity mobile game development?
// I have found this article: https://medium.com/aimonks/8-valuab...ur-unity-mobile-game-development-2e856b05e079

Are your making a big game?
If it's not so big or complex. You could consider Kotlin/Java + Libgdx along with Ktor or Spring Boot on the backend side