SwiftUI is good, albeit not without issues, as long as you tolerate them. The same is true for any approach. My most recent app was built in SwiftUI because I have been using React Native in my professional work for so long I wanted a change of scenery.
Each approach has its issues, and it all boils down to a matter of preference and which tradeoffs are appropriate for the project.
That is, pure native apps, can integrate KMP libraries. They cannot integrate Flutter libraries.
In other words, if I write a KMP library, I can ship it for multiple platforms and developers can use it in their Flutter project, or in their pure Android/Kotlin project, or in their pure iOS project.
If KDE can develop a high performance stable desktop, you can design whatever.
I don't know what your experience is, and I mean no offence or anything, but the only people I have seen who were happy with Qt for mobile development were people who had never tried to do it with a modern language, like Kotlin.
With Compose Multiplatform and Kotlin Multiplatform, you can write a cross-platform app in a modern language, and that is far better than C++.
All that to say, I don't think that vibe-porting will give you more than cross-platform. With cross-platform, at least your engineers understand the codebase.