Using the information at https://docs.telerik.com/devtools/wpf/controls/radwindow/how-to/use-radwindow-as-user-control works well for using the RadWindow with Prism.
However, it appears that the window is not using the color variation of the theme. I would like to switch dynamically from Light to Dark, but have been unsuccessful.
In the App.xaml.cs in OnStartup, the first line is:
Other controls change to this theme, but not the Main Window.