There has long been needs for a simple Qt frontend for pulseaudio-based audio mixer. So I ported the gtk+ version pavucontrol program to Qt5 for use in LXQt. Here is a screenshot.
The source code is here. https://github.com/lxde/pavucontrol-qt
Since the original source code of pavucontrol is written in C++, it becomes trivial to port it to Qt. The whole porting process took me two days only. Porting programs from gtk+ 3 to Qt 5 is not really that difficult as long as you know how to do it. You see the proof. 🙂