I figured it out. To be honest this ContentView was the original XCode generated view, but what I did not take into account that I created and added a new file with some model structs in it. And it the model there was pproperty which was named Image (I usually use app.quicktype.io to generate structs from JSON). This Image struct was in conflict with the SwiftUI original Image struct. And XCode got just confused rather than warning me about the conflict. Thank you for thinking about my problem!

15.1, the last stable version. When I reverted to the 15.0.1 version it worked again. But it was scary to see in my project I'm working on, that everything fell apart. Dozens of errors like these popped up. It's not my code by the way, it's the starting project of XCode. Just wanted to show that the problem is not code dependent. Maybe the XCode does not find something, some settings or some library.