title: Xcode 11 backward compatibility: "UIWindowScene is only available in iOS 13 or newer"
body: <p>In Xcode 11, I created a new app project from the Single View App template. I want this app to run in iOS 12 as well as iOS 13. But when I switch the deployment target to iOS 12, I got a lot of error messages like this one:</p>
  
  <blockquote>
    <p>UIWindowScene is only available in iOS 13 or newer</p>
  </blockquote>
  
  <p>What should I do?</p>