I converted some old Objective-C code to the Swift equivalent & then further changes were required with visionOS. Also, the UI Kit application is using storyboards.

I also wanted to be able to present 3D content in a volumetric view along side to the UI Kit view controllers.

Adding 3D content to your app | Apple Developer Documentation

Plist changes

• with visionOS, you can specify the default scene type for the role, I managed to get it working without this - does it default to use plain window style?

• as there will be multiple window groups in visionOS:

  

UI Kit - app code

import UIKit
import AVFoundation

@main
class WHAppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Setting the cache size for the app; this should be re-evaluated.
        // The app currently downloads JSON from Bands in Town.
        let URLCache = Foundation.URLCache(memoryCapacity: 4 * 1024 * 1024,
                                           diskCapacity: 20 * 1024 * 1024,
                                           diskPath: nil)
        Foundation.URLCache.shared = URLCache

        // Configure the audio categories for the app; this can change
        // if the user selects the audio mixer scene.
        setAudioCategories()
        setAppAppearance()

        return true
    }
}

visionOS - app code