In WinUI3, how can I put a TeachingTip in a ContentDialog?

The code below does not show a teaching tip-does anyone know how to make one show?

<Window
    x:Class="WinUI3App.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="using:WinUI3App"
    xmlns:muxc="using:Microsoft.UI.Xaml.Controls"
    mc:Ignorable="d"
    Title="WinUI3App" Height="450" Width="800">

    <Grid>
        <Button Content="Open Dialog" HorizontalAlignment="Center" VerticalAlignment="Center" Click="Button_Click"/>
    </Grid>
</Window>

using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;

namespace WinUI3App
{
    public sealed partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private async void Button_Click(object sender, RoutedEventArgs e)
        {
            ContentDialog dialog = new()
            {
                Title = "Sample Content Dialog",
                CloseButtonText = "Close",
                XamlRoot = (sender as Button).XamlRoot
            };

            TextBlock text = new() { Text = "Hello world" };

            TeachingTip teachingTip = new()
            {
                Content = "This is a sample teaching tip.",
                Title = "Sample Teaching Tip",
                Target = text,
            };

            dialog.Content = new StackPanel()
            {
                Children =
                {
                    text,
                    teachingTip
                }
            };

            dialog.Opened += (s, _) => teachingTip.IsOpen = true;
            dialog.Closed += (s, _) => teachingTip.IsOpen = false;

            await dialog.ShowAsync();
        }
    }
}

I guess you can't show a ContentDialog and a TeachingTip at the same time. Let me show you another way to do this by creating a custom dialog based on a Window:

CustomDialog.cs

using Microsoft.UI.Xaml;
using System.Threading.Tasks;
using WinUIEx;

namespace App1;

public enum CustomDialogResult
{
    Cancel,
    OK,
}

public partial class CustomDialog : WindowEx
{
    private TaskCompletionSource<CustomDialogResult>? _taskCompletionSource;

    public CustomDialog()
    {
        this.InitializeComponent();
        this.IsAlwaysOnTop = true;
        this.CenterOnScreen();
        this.SetWindowStyle(WindowStyle.Caption);
    }
    public new object? Content { get; set; }

    public Task<CustomDialogResult> ShowAsync()
    {
        this.ContentPresenter.Content = Content;
        _taskCompletionSource = new();
        this.Activate();
        return _taskCompletionSource.Task;
    }

    private void OKButton_Click(object sender, RoutedEventArgs e)
    {
        _taskCompletionSource?.SetResult(CustomDialogResult.OK);
        this.Close();
    }

    private void CancelButton_Click(object sender, RoutedEventArgs e)
    {
        _taskCompletionSource?.SetResult(CustomDialogResult.Cancel);
        this.Close();
    }
}

CustomDialog.xaml.cs

<ex:WindowEx
    x:Class="App1.CustomDialog"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:ex="using:WinUIEx"
    xmlns:local="using:App1"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Width="300"
    Height="200"
    mc:Ignorable="d">

    <Grid
        RowDefinitions="*,Auto">
        <ContentPresenter
            x:Name="ContentPresenter"
            Grid.Row="0" />
        <Grid
            Grid.Row="1"
            ColumnDefinitions="*,*">
            <Button
                Grid.Column="0"
                Click="OKButton_Click"
                Content="OK" />
            <Button
                Grid.Column="1"
                Click="CancelButton_Click"
                Content="Cancel" />
        </Grid>
    </Grid>
</ex:WindowEx>

then use it like this:

public sealed partial class MainWindow : Window
{
    public MainWindow()
    {
        this.InitializeComponent();
    }

    private async void Button_Click(object sender, RoutedEventArgs e)
    {

        TextBlock text = new() { Text = "Hello world" };

        TeachingTip teachingTip = new()
        {
            Content = "This is a sample teaching tip.",
            Title = "Sample Teaching Tip",
            Target = text,
            IsOpen = true,
        };

        CustomDialog dialog = new();
        dialog.Content = new StackPanel()
        {
            Children =
            {
                text,
                teachingTip
            }
        };

        CustomDialogResult result = await dialog.ShowAsync();
    }
}

NOTE:

I'm using the WinUIEx NuGet package here but you should be able to do this without it.