The solution was to use it on appear, like so:

@main
struct ExampleApp: App {

    @UIApplicationDelegateAdaptor private var appDelegate: AppDelegate
    
    var body: some Scene {
        WindowGroup {
            ContentView()
                .onAppear(perform: {
                    appDelegate.app = self
                })
        }
    }
}

And inside AppDeligate it should start like this:

class AppDelegate: NSObject, UIApplicationDelegate {
    
    var app: ExampleApp?