Qt Quick items in QQuickWidget does not handle palette changes in some cases:

• Background color is not set according light/dark mode, and is not updated on light/dark mode change
  https://codereview.qt-project.org/c/qt/qtdeclarative/+/683641

• Accent color for the focus rect is not updated on OS settings change (macOS)

• Window active state is not propagated.

Screenshot on macOS showing some of the issues below. Some of these also reproduce for a stand-alone QQuickView.