Wow you're comparing very different tool sets here and it all depends on what exactly your app does
For desktop, GTK and QT are by far the better options as they allow full window management and control from the ground up and can design exactly what you want, the way you want it.
Godot simply ignores all that micromanagement and lets you focus on the functionality of your app which is great for mobile users, not having to meddle with canvases and fragments or activities
If your goal is simply to make your app multi-platform again it really depends on what your app does as all 3 options can provide equally satisfying results