force UISplitViewController orientation to landscape on iPad

Question

I am struggling to get my UISplitViewController to always stay in landscape mode. The mothods that work with other ViewControllers don't seem to work here.

In my AppDelegate I have:

var supportedInterfaceOrientation: UIInterfaceOrientationMask = .all
func application(_ application: UIApplication, supportedInterfaceOrientationsFor window: UIWindow?) -> UIInterfaceOrientationMask {
        return supportedInterfaceOrientation
    }

In my UISplitViewController I have:

let appDelegate = UIApplication.shared.delegate as! AppDelegate
    
override func viewDidLoad() {
    super.viewDidLoad()
    appDelegate.supportedInterfaceOrientation = .landscapeLeft
    UIDevice.current.setValue(UIInterfaceOrientation.landscapeLeft.rawValue, forKey: "orientation")
}

deinit {
    appDelegate.supportedInterfaceOrientation = .all
}

override var shouldAutorotate: Bool {
    return false
}

override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
    return .landscapeLeft
}

override var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation {
    return .landscapeLeft
}

And I am presenting my UISplitViewController like this:

let vc = self.storyBoard.instantiateViewController(withIdentifier: "CompareSplitVC") as! CompareSplitViewController

vc.modalPresentationStyle = .fullScreen
self.present(vc, animated: true, completion: {})

All of this has no effect and one of these are being called: shouldAutorotate, supportedInterfaceOrientations, preferredInterfaceOrientationForPresentation

What am I doing wrong?

Edit: I am getting this issue on iPad but not on iPhone.