// add this line to WinUiPlot() method in WinUIPlot.cs
        Loaded += WinUIPlot_Loaded;
//then created a handler for it this is called after initialization of the WinUiPlot to get proper display scale
    private void WinUIPlot_Loaded(object sender, RoutedEventArgs e)
    {
        if (XamlRoot != null)
        {
            XamlRoot.Changed += DetectDisplayScale; ;
            Plot.ScaleFactor = XamlRoot.RasterizationScale;
            DisplayScale = (float)XamlRoot.RasterizationScale;
        }
    }
// and also handler for detect display scale it is called when user move application from monitors with different scale
    private void DetectDisplayScale(XamlRoot sender, XamlRootChangedEventArgs args)
    {
        if (XamlRoot != null)
        {
            Plot.ScaleFactor = XamlRoot.RasterizationScale;
            DisplayScale = (float)XamlRoot.RasterizationScale;
        }
    }