It is very hard to say what are the changes in general.
Major ones are due to scene support but there may be other ones.
Another to use App Development with Swift, but it dates 2017, so same issue
« App Development with Swift. » Apple Inc. - Education, 2017.
There are many good tutorials (notably Ray Wenderlich), but they are focused on specific topic, not general overview : search for instance 'Ray Wenderlich scene management'
For this forum, the best is to ask specific question when you have a problem with some code. Someone will surely help.
The AppCoda tutorial you linked to is fine. The mistake you made was you didn't choose Storyboard from the User Interface menu when you created the project so you ended up with a SwiftUI project. The AppCoda tutorial does not use SwiftUI, which is why you're running into problems. Create a new project and make sure you choose Storyboard from the User Interface menu. If you don't explicitly choose Storyboard, you'll end up with a SwiftUI project.
Read the article at the following URL for more detailed information about avoiding creating SwifUI projects in Xcode 11:
Yep, the big thing I didn't know when making this post was that SwiftUI was a (relatively new) thing and an alternative to storyboard. I've since decided to get stuck into SwiftUI having found some good resources (including Apple's) as it seems a good investment at the risk of less help and documentation since it's new.