The weird result comes mainly from the very strongly opinionated Gnome/GDM devs IMHO.
As a note, there are two things that need to be separated:
- GDM: on Wayland or on Xorg
- Gnome: on Wayland or on Xorg
IIUC Archwiki/GDM, there is also a udev rule for that.
I think you will find the linked article interesting, if not already read.
If QT_QPA_PLATFORMTHEME
is not properly set to qt5ct
(if I’m not wrong), and set the kvantum
as controler in Qt5ct settings, you wouldn’t be able to control Qt5/6 settings with Kvantum, AFAIK from experience (but have not been using Gnome lately).