ring-kde uses the material style by default even when run on my KDE Plasma desktop. I need to run `QT_QUICK_CONTROLS_STYLE=org.kde.desktop ~/kde/usr/bin/ring-kde` to force it to use the Breeze style. This should happen automatically.
The material style is no longer used on desktop Linux. There is now the proper infrastructure to compile different qtquickcontrols2 config file for each platforms.