Ask HN: What Architecture Apple uses in its iOS Apps?

I am curious what SW architecture(s) were used for development of the system iOS apps like Messages, Photos, App Store, etc.

I would assume that with the more complex apps, a simple MVC/MVVM is not scalable enough and alternatives like VIPER and VIP (or a completely custom architecture) may be used. Does Apple use the new SwiftUI and Combine Frameworks?