In iOS15, I receive the following warning:

'windows' was deprecated in iOS 15.0: Use UIWindowScene.windows on a relevant window scene instead

When I try to use UIWindowScene, I am warned that I need to use a value type. But however, I get init() not available when I try to do that.

Here's my use case below

func overrideDisplayMode() {
    var userInterfaceStyle: UIUserInterfaceStyle
    let overrideUserInterfaceStyle = UIWindowScene()  // init() not available

    switch displayMode {
    case .dark:
        userInterfaceStyle = .dark
    case .light:
        userInterfaceStyle = .light
    case .system:
        userInterfaceStyle = UITraitCollection.current.userInterfaceStyle
    }

    UIWindowScene.windows.first?.overrideUserInterfaceStyle = userInterfaceStyle // replacement for below, but I get error for not using a value type

    UIApplication.shared.windows.first?.overrideUserInterfaceStyle = userInterfaceStyle // deprecated
}

How to fix this?

Try this:

let scenes = UIApplication.shared.connectedScenes
let windowScenes = scenes.first as? UIWindowScene
let window = windowScenes?.windows.first