On Linux/Wayland, After using DragHandler with window.startSystemMove, the first click or mouse hover effects before the first click are not working within the Webengine area. After clicking inside the app or elsewhere, clicks and hover effects start to work.
To reproduce, add the below code to menuBar in quicknanobrowser/BrowserWindow.qml.

background: Rectangle {

      color: "#111"
      width: parent.width

      height: 40
      
      DragHandler {
        onActiveChanged: {
          if (active)
            browserWindow.startSystemMove();
        }
        target: null
      }
}