I haven't found a solution for disabling the menu other than the solution that @andreimarincas shared, but if anyone else is coming to this post for a way to hide the back button title while still showing titles in the menu, there is an easier way than what that post mentions, using UINavigationItem.BackButtonDisplayMode - https://developer.apple.com/documentation/uikit/uinavigationitem/backbuttondisplaymode. Setting this property (new in iOS 14) to .minimal will only show the back button indicator instead of the title. I've been able to make this work nicely by putting the following in viewDidLoad:
if #available(iOS 14.0, *) {
self.navigationItem.backButtonTitle = "Custom menu title"
self.navigationItem.backButtonDisplayMode = .minimal
} else {
self.navigationItem.backBarButtonItem = UIBarButtonItem(title: "", style: .plain, target: nil, action: nil)
}
The value you set for backButtonTitle will only show in the navigation menu, and you can still hide the title if iOS 14 is not available.