Вот фиксированный вариант
struct ContentView: View {
var body: some View {
NavigationView{
List(
[
Course(name: "sample1", imageUrl: "no image"),
Course(name: "sample2", imageUrl: "no image")
], id: \.name // << here !!
){
Text($0.name)
}.navigationBarTitle(Text("Courses"))
}
}
}