Not really what you are asking for, but I have been working on this library for the last year GitHub - gen2brain/iup-go: Cross-platform UI library with native controls · GitHub (still not fully ready for release, almost there). The same app can be compiled for Win32, WinUI3, Cocoa, GTK2, GTK3, GTK4, Qt5, Qt6, FLTK, EFL, GNUStep, Haiku, WebAssembly, Android, and iOS. I guess everything is covered, and I answered the famous “but what is the native UI on Linux” question. Of course, you can use C or C++; there is a nice C++ wrapper that is maintained.
I just shared an app I did here, Comic Book Converter.