[fingerlocks]

Not sure I follow. Have you seen UIViewRepresentable? You can turn a UIView into a SwiftUI view in 5 lines of code. If you need to move state there is a two way bridge you can choose to implement called a Coordinator. It is a blank protocol with zero obligations to fulfill and only exists as convenient a reference type simultaneously accessible by both the UIView and the SwiftUI parent.

I can’t imagine how it could be implemented more simply.

Even if you are rendering a complex chain of compute shaders with multistage heap fences onto a process shared IOSurfaceRef with several concurrent threads greedily realiasing your scratch buffer to queue up more work, it doesn’t matter. Eventually you’ll up with a UIView or CALayer and it’s still just one function call to bring it into SwiftUI.