Use the org.freedesktop.appearance interface to implement a desktop-agnostic solution on Linux.

The current implementation relies on GNOME-specific interfaces, which may introduce unnecessary dependencies or fail to work properly on certain desktop environments. Using the org.freedesktop.appearance interface provides a desktop-agnostic solution.

For reference, see the following links:
https://flatpak.github.io/xdg-desktop-portal/docs/doc-org.freedesktop.portal.Settings.html