Earlier quoted context omitted.
That information is already available, and much of the implementation (if not all) is open source. You’re free to produce your own toolchain, developer tools, IDE, etc. This generally isn’t done because it’s a significant amount of work, and you’ll always be playing catch-up to Apple’s comprehensive integrated development stack.
The fact that you need a MacOS machine even to build Xamarin or React native apps always struck me as bizarre though - I assumed there was some proprietary component that Apple wouldn't publish the details for.
It’s a large amount of expensive, ongoing work, and leveraging Apple’s native toolchain will invariably provide a better user experience.