Android app PushAsync nav not working after Xamarin.Auth oidc completes

Question

I have created a Xamarin.Forms app that authorizes and authenticates using our Identity Server. The whole auth process works well in both iOS and Android - in both cases I get a token and can query our API.

The Android app does not accept navigation commands and stays "stuck" on the target activity for the custom URI callback.

The android manifest has an activity entry for is4.callback and it works well:

    // The Name property here is referred to in the Activity in Android.manifest
    // https://learn.microsoft.com/en-us/xamarin/android/platform/android-manifest
    [Activity(Name = "is4.callback")]
    public class AuthCallback : Activity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);

            if (Intent?.Data?.ToString() != null)
            {
                // Convert Android.Net.Url to Uri
                var uri = new Uri(Intent?.Data?.ToString());

                // Load redirectUrl page
                AuthenticationState.Authenticator.OnPageLoading(uri);

                //this.Finish();
                //return;

            } else
            {
                // deal with it
            }

        }
    }

The OnPageLoading() method call above sends control back to OnAuthCompleted() per Xamarin.Auth as expected:

        async void OnAuthCompleted(object sender, AuthenticatorCompletedEventArgs e)
        {
            if (e.Account != null && e.Account.Properties != null)
            {
                Client.DefaultRequestHeaders.Add("Authorization", $"Bearer {e.Account.Properties["access_token"]}");

                HttpResponseMessage response = await Client.GetAsync("https://our.is4.server/connect/userinfo");
                if (response != null)
                {
                    using (HttpContent content = response.Content)
                    {
                        string responseBody = await response.Content.ReadAsStringAsync();
                        Console.WriteLine(responseBody);
                    }
                    Console.WriteLine(_logStringPre + "MainPage.OnAuthCompleted(), calling nav:");
                    await Navigation.PushAsync(new HasAuth());
                }
                else
                {
                    // deal with it
                }
            }
            else
            {
                await Navigation.PushAsync(new NoAuth());
            }
        }

However, for Android that PushAsync to the HasAuth view doesn't happen as expected - the Activity that catches the call back (is4.callback) retains the focus. The little "back" < button at the bottom of the screen on my Pixel 3 sends me to the HasAuth page, where the view should be, though. That last WriteLine prior to PushAsync does fire, I think I need to close the Android activity somehow?

The use of finish() in is4.callback prevents auth from happening. return in that activity seems to have no effect at all.

I do see the "If CustomTabs Login Screen does not close automatically..." suggestion from the Android OS, visible over the is4.callback activity, but it looks to me like CustomTabs closed correctly? What am I missing?

Thanks!