Black screen after adding SceneDelegate and updating Info.plist

You have several issues here. It's important to read the documentation related to the app lifecycle which states what is called under iOS 13 and what is called under iOS 12.

You may also want to see my Single View App template that supports iOS 12 and 13.

Looking at your code, here is a summary of the problems:

AppDelegate:

• You should only setup the main window and the root view controller if the app is being run under iOS 12 or earlier. You need to check this at runtime.
• The func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) method should not be in the app delegate.
• Not directly related but never sleep on app startup. Remove the Thread.sleep(forTimeInterval: 3.0) line. Users want to use your app, not stare at the launch screen longer than necessary. And blocking the main thread on app launch can cause your app to be killed.

SceneDelegate:

• This is mostly fine but there is no reason for the guard let _ = (scene as? UIWindowScene) else { return } line, especially since it is inside an if let that already does that check.
• You don't appear to be using SwiftUI so remove that import.

I would update your app delegate to be more like this:

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?

    func application(_ application: UIApplication, willFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? = nil) -> Bool {
        UINavigationBar.appearance().barTintColor = UIColor(red:0.08, green:0.23, blue:0.62, alpha:1.0)

        if #available(iOS 13.0, *) {
            // In iOS 13 setup is done in SceneDelegate
        } else {
            let window = UIWindow(frame: UIScreen.main.bounds)
            self.window = window

            if (user != nil && userSelfIdent != nil){
                let mainstoryboard:UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
                let newViewcontroller:UIViewController = mainstoryboard.instantiateViewController(withIdentifier: "swrevealviewcontroller") as! SWRevealViewController
                window.rootViewController = newViewcontroller
            }
        }

        return true
    }

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        if #available(iOS 13.0, *) {
            // In iOS 13 setup is done in SceneDelegate
        } else {
            self.window?.makeKeyAndVisible()
        }

        return true
    }

    func applicationWillResignActive(_ application: UIApplication) {
        // Not called under iOS 13 - See SceneDelegate sceneWillResignActive
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
        // Not called under iOS 13 - See SceneDelegate sceneDidEnterBackground
    }

    func applicationWillEnterForeground(_ application: UIApplication) {
        // Not called under iOS 13 - See SceneDelegate sceneWillEnterForeground
    }

    func applicationDidBecomeActive(_ application: UIApplication) {
        // Not called under iOS 13 - See SceneDelegate sceneDidBecomeActive
    }

    // MARK: UISceneSession Lifecycle

    @available(iOS 13.0, *)
    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
        // Called when a new scene session is being created.
        // Use this method to select a configuration to create the new scene with.
        return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
    }

    @available(iOS 13.0, *)
    func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
        // Called when the user discards a scene session.
        // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
        // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
    }
}

Your scene delegate could be like:

@available(iOS 13.0, *)
class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    var window: UIWindow?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        guard let windowScene = (scene as? UIWindowScene) else { return }

        let window = UIWindow(windowScene: windowScene)
        self.window = window

        if (user != nil && userSelfIdent != nil){
            let mainstoryboard:UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
            let newViewcontroller:UIViewController = mainstoryboard.instantiateViewController(withIdentifier: "swrevealviewcontroller") as! SWRevealViewController
            window.rootViewController = newViewcontroller
            window.makeKeyAndVisible()
        }
    }

    func sceneDidDisconnect(_ scene: UIScene) {
        // Called as the scene is being released by the system.
    }

    func sceneDidBecomeActive(_ scene: UIScene) {
        // Not called under iOS 12 - See AppDelegate applicationDidBecomeActive
    }

    func sceneWillResignActive(_ scene: UIScene) {
        // Not called under iOS 12 - See AppDelegate applicationWillResignActive
    }

    func sceneWillEnterForeground(_ scene: UIScene) {
        // Not called under iOS 12 - See AppDelegate applicationWillEnterForeground
    }

    func sceneDidEnterBackground(_ scene: UIScene) {
        // Not called under iOS 12 - See AppDelegate applicationDidEnterBackground
    }
}

Steps for running with iOS 13 and lower versions:

1. Change deployment target to iOS 12.

2. Replace the AppDelegate's methods with what they ought to have for iOS 12 development. Also add this:

   var window: UIWindow?
   

3. Remove SceneDelegate.

4. Remove Application Scene Manifest in your info.plist.

It will work on both iOS 13 and lower iOS Version

Easily follow these steps:

1. Remove scene delegate file

2. Add below code to AppDelegate.swift

    class AppDelegate: UIResponder, UIApplicationDelegate {
   
    var window: UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        return true
    }
   }
   

3. Remove the Application Scene Manifest line from your .plist file

   

I commented 2 scene methods in the AppDelegate, and then it works please check my screenshot