[Bug] The `Qt::ColorScheme` is always `Light`, despite my global preference.

Even with `org.gtk.Gtk3theme.Breeze` installed, and `lookandfeeltool -a org.kde.breezedark.desktop`, VueScan's `Qt::ColorScheme` remains `Light`:

Considering that `org.freedesktop.appearance.color-scheme` exposes this outside of Qt, even wxWidgets should be able to consume it.

#### My Environment

1.

~~~sh
#!/usr/bin/env sh
flatpak info app/io.github.Foldex.AdwSteamGtk/x86_64/stable
~~~

1.

~~~YAML
ID: com.hamrick.VueScan
Ref: app/com.hamrick.VueScan/x86_64/stable
Arch: x86_64
Branch: stable
Version: 9.8.01
License: LicenseRef-proprietary
Origin: flathub
Collection: org.flathub.Stable
Installation: system
Installed Size: 8.2 MB
Runtime: org.gnome.Platform/x86_64/49
Sdk: org.gnome.Sdk/x86_64/49

Commit: 968d9e9430a535bea660482dac51454965720e576925332c6dedf081c68dca49
Parent: 2e54076ce5c04141450926753f00b4cfb1e3d0b0f9607cc999c6097e040dfa88
Subject: vuescan: Update vuescan.tgz (b434b57fc8e9)
Date: 2026-05-19 11:32:51 +0000
~~~

No source file, test, or entry point is named in the report. Begin by identifying where the Flatpak application handles desktop appearance settings, then verify the reported KDE color preference against Qt::ColorScheme and org.freedesktop.appearance.color-scheme. Done means the application reflects the configured dark preference instead of remaining Light.

Written by the indexing model from the issue text.