MenuFlyout ItemTepmplate still not applied

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MenuFlyout ItemTepmplate does not gets applied:
With Avalonia 0.10.18 the items are plain shown in UI as ToString()

With Avalonia 11.0.0-preview5 it is complete broken and nothing is shown:
[Binding]Error in binding to 'Avalonia.Controls.MenuFlyout'.'Items': 'Null value in expression '{empty}' at ''.'(MenuFlyout #5560998)

My Window xaml looks like this:

<Button Content="Testen">
    <Button.Flyout>
	    <MenuFlyout Placement="Left" Items="{Binding Path=TestItems,Mode=OneWay}">
		    <MenuFlyout.ItemTemplate>
			    <DataTemplate>
				    <TextBlock Text="{Binding Path=Name,Mode=OneWay}" />
			    </DataTemplate>
		    </MenuFlyout.ItemTemplate>
	    </MenuFlyout>
    </Button.Flyout>
</Button>

And the ViewModel looks like this:

public record class TestItem(string Name, string Info);

public class MainWindowViewModel
{
    public MainWindowViewModel()
    {
        TestItems = new ObservableCollection<TestItem>
        {
            new TestItem("Hallo", "Hallo Welt"),
            new TestItem("Bla", "Hallo Welt"),
            new TestItem("Blubb", "Hallo Welt"),
            new TestItem("Etwas mehr Text", "Hallo Welt"),
            new TestItem("Hallo Ihr da", "Hallo Welt")
        };
    }

    public ObservableCollection<TestItem> TestItems { get; }

Desktop (please complete the following information):

• OS: Windows 10 Pro 21H2 64 Bit