I mean, hang on there... Objective-C, while probably frustrating to get started with, is literally "just about C". Projects have been doing Objective-C interop for decades now, very similar to what is being done in the posted article. It's not really gated off at a programming layer, moreso in how Apple's been so frustrating about developing on non-Apple hardware.
It's not exactly what I would call "hostile", language-wise. Swift, on the other hand, might be a bigger barrier...
Yeah, bindings for UIKit aren’t actually all that challenging to write. There’s quite a number of UIKit apps written at least partially in languages other than Obj-C/Swift.
Android Framework on the other hand is not great in this department. Practically speaking it’s just Java and Kotlin. I wish I could write Swift there because even if Kotlin is similar syntactically the JVM baggage can be irritating.
It's not exactly what I would call "hostile", language-wise. Swift, on the other hand, might be a bigger barrier...