I have built a functional application (iOS & Android) using react-native which has a large amount of audience on the market and is working great. However, now the companies approach me and ask to create an SDK of a my application's part functionality for their use. The part should be working as a library for native applications (I suppose Swift/Kotlin)

I was thinking to create a react-native library for Android and iOS using js, but I could not find an answer online on how to do it. At first, I thought that I could use npm, but it is not a correct way to use libraries on native applications.

If I would want a part of my react-native app in some native Android/iOS application, should I write a native SDK library using Kotlin/Swift? Or, is there a simpler approach, e.g using react-native?