Black or Greyscale splash screen during Qt apps startup under Gnome3

Hi,

It's my first bug report here, and I'm not a developer, so my apologies in advance if this bug is not very well reported !
Please particularly correct the component if it's not matching.

Since a while under the Gnome 3 environment, I have every time a black splash screen launching Krita, and most of the time a greyscale splash screen launching Scribus, with Qt 4.8.6 installed.
Please see the 2 short videos attached.

I originally reported this bug for Krita here : https://bugs.kde.org/show_bug.cgi?id=344344
As Boudewijn suspect a Qt bug, and he is far more experienced than me, I report the bug here instead of the Gnome bugzilla.

I tried to disable color management in Gnome, to disable color management in Krita, to disable OpenGL, to delete my preference folder (~/.kde4/share/apps/krita) and kritarc file... And I only obtained once (deleting the preference folder and not the kritarc file) to see correctly the splash screen, but can't reproduce it anymore.
Tried with Gnome on Wayland, and Gnome Classic, and the bug is also present.

It may be a video driver (radeon) bug linked to Qt.