Some Qt applications partially get system theme

Xfce 4.16, Greybird-dark theme.

Some (not all) Qt applications, doesn’t get the system theme, like showed in the following screenshot:

The theme is not applyed in the menu bar, but another application, shows the issue in the save dialog window: flameshot:


Some other Qt apps, like xnviewmp, doesn’t get the system theme at all.

I tried to force the theme, by executing these applications using GTK_THEME=Greybird:dark $appname but with no dice. And the same occurs also with others themes.

What can I try to do?

qt-based applications must be themed separately by way of kvantum-qt5.

Yes, I am aware of kvantum-qt5, but why some QT applications get the system theme and some other partially or not at all?
There is Greybird-dark for kvantum?

I’m not sure. I can only find the regular (light) variant. :arrow_down: