I'm not a fan of Qt from my time at Dropbox (we used it for our desktop client preferences for some time), but will need to check out GTK4 and Compose. Thanks!
I used to be a big Qt fan but I have started favoring Gtk. Glade is better than any Qt designer. And being C based you tend to get better Gtk bindings in other languages. Who wants to develop in C++ these days unless they are doing systems programming?
My strategy would be Cocoa for MacOS/iOS and Gtk for Linux/Windows.
I don't really dev with Qt, but I thought a lot of folks were using QML and sometimes QtQuick these days. Seems to make it possible to hide a lot of the C++ :)
Although of course, it does mean you probably have to touch C++ sometimes.