It works with QT5 apps, but not with QT6.

(This works correctly on Fedora 36, for example.)

adwaita-qt6 is installed.

How I got this problem:

1. mkvtoolnix-gui built with qt5 on tumbleweed is now completely broken on
Gnome. The maintainer has now built it with qt6 to fix the problem (like
everyone else: Fedora 36, archlinux, ... are all building it with qt6)
https://build.opensuse.org/package/show/home:alois:branches:multimedia:apps/mkvtoolnix.qt6

(His computer broke down, so it will take a couple days until he can push this
to the default repo: https://bugzilla.opensuse.org/show_bug.cgi?id=1202446 )

2. To get the Gnome theme to apply, I have to do:

> mkvtoolnix-gui -style adwaita-dark

Expected behavior:
The theme should be applied automatically, like it does with qt5.

Thanks for fixing this.