[Plasma 6, X11] Windows with popup dialogs become white/desaturated

[ericr35811]

When a window creates a popup dialog (like closing Konsole while a process is running, closing KWrite without saving, etc.), the window becomes completely desaturated, including the contents, widgets, and window decorations. This only occurs on X11, on Wayland it seems to be fine.

If I turn off the "Dialog Parent" desktop effect, which darkens windows behind dialogs, the issue goes away. It also goes away if I keep Dialog Parent and disable LightlyShaders. Turning the custom blur effect on or off has no impact. So it feels like LightlyShaders is interacting with Dialog Parent somehow.

Wayland:

X11:

I have a Kvantum theme applied, but I tried turning it off and the problem is still there with Breeze.

I got this warning several times while compiling, but I don't know if it's relevant:
cc1plus: warning: /usr/include/qt6/QtCore/6.7.0/QtCore: not a directory

[akano12]

duplicate of #139