FirebaseUI "Sign in with email" does nothing when tapped - swift

Question

I have the following code taken directly from this blog. This code successfully displays the FirebaseUI with Google sign In, Apple sign In, and Email sign in when I place the SignInViewUI into my view.
Google and Apple sign in both function correctly. Email sign in does nothing when tapped.
import Firebase
import FirebaseUI
import SwiftUI
typealias AM = AuthManager
class AuthManager : NSObject{
static let shared = AuthManager()
var authViewController : UIViewController {
return MyAuthViewController(authUI: FUIAuth.defaultAuthUI()!)
}
init(withNavigationBar : Bool = false){
FirebaseApp.configure()
super.init()
self.setupProviders()
}
private func setupProviders(){
let authUI = FUIAuth.defaultAuthUI()!
let providers: [FUIAuthProvider] = [
FUIGoogleAuth.init(authUI: authUI),
FUIOAuth.appleAuthProvider(),
FUIEmailAuth()]
authUI.providers = providers
}
}
extension AuthManager {
// an optional handler closure for error handling
func signOut(onError handler : ((Error?) -> Void)? = nil ){
do {
try FUIAuth.defaultAuthUI()?.signOut()
if let handler = handler {
handler(nil)
}
}
catch (let err){
if let handler = handler {
handler(err)
}
}
}
func isSignedIn() -> Bool {
if let _ = Firebase.Auth.auth().currentUser{
return true
}
return false
}
}
extension AuthManager {
func setAuthDelegate(_ delegate : FUIAuthDelegate){
FUIAuth.defaultAuthUI()?.delegate = delegate
}
}
class MyAuthViewController : FUIAuthPickerViewController {
override func viewDidLoad() {
super.viewDidLoad()
let scrollView = view.subviews[0]
scrollView.backgroundColor = .clear
let contentView = scrollView.subviews[0]
contentView.backgroundColor = .clear
view.backgroundColor = .clear
}
}
struct SignInViewUI: UIViewControllerRepresentable {
func makeUIViewController(context: UIViewControllerRepresentableContext<SignInViewUI>) ->
UIViewController {
return AM.shared.authViewController
}
func updateUIViewController(_ uiViewController: UIViewController,
context: UIViewControllerRepresentableContext<SignInViewUI>) {
// empty
}
}

Answer 1

I believe this is something to do with a navigation controller being required for the Email sign in, based on the final comment on this GitHub issue.
Surrounding the SignInViewUI in a NavigationView allows the button to work.
Secondly, the FirebaseApp.configure() line must be removed from the AuthManager and placed into the AppDelegate application(_ application: UIApplication, didFinishLaunchingWithOptions ... method.