UISearchContainerViewController exists both on tvOS and on iOS. Apple has sample code showing how to use it in tvOS: they configure a UISearchController, hand it to a UISearchContainerViewController, wrap that in a UINavigationController, and make it one of a UITabBarController's children.
But I have never seen an example of UISearchContainerViewController on iOS, and I can't make it work there. For example, I do exactly what Apple does, except that I push the UISearchContainerViewController onto a navigation stack, or I wrap it in a navigation controller and present it, or whatever; and there's no search field so the whole thing is useless.
Has anyone ever gotten UISearchContainerViewController to do anything useful on iOS?