It's kind of hard to explain whats wrong. But when running the attached QMLPreviewer project, which is a modified version of the classic qml previewer example, and applying a contrast theme (e.g. Aquatic), the QQuickWindow palette won't change to use the expected colors.

If the contrast theme is applied, before starting the application, the palette colors are set correctly.

Note that the palette is normally updated correctly for most of our QML examples, this is an edge case, where it's not working.

Another issue, not directly related to the one above, is that running a Qt Quick Controls application, using the FluentWinUI3 style, under a QApplication, causes the highlightedText color to be wrong.