> So it will be Kotlin for business logic and Flutter for UI? It is possible, I've heard of it being done by others but I don't have a huge amount of experienc

> So it will be Kotlin for business logic and Flutter for UI? It is possible, I've heard of it being done by others but I don't have a huge amount of experience with Flutter and last time I looked interop was a bit tedious in Flutter. I'm also not sure if you would gain all that much from using Kotlin in that case, rather keep everything in Dart / Flutter? In the case of the last contracting job I did I used native UI frameworks from Android and iOS with a shared Kotlin framework doing business logic. Depending on your use case and experience (and if you have time for it) I'd encourage building some small tests or proof of concepts in each option and evaluate.