@sschmitt, did you find out any solution to this?
Looking into the documentation of CPTemplateApplicationSceneDelegate method,
templateApplicationScene(:didConnect:to:) says
@note This method is provided only for navigation apps; other apps should use the variant that does not provide a window.
So I am assuming CPWindow is not accessible for non-navigation Carplay apps. Which seems to contradict the official answer of ricob.
What are your thoughts on this?