How to bind RadioButtonGroup.SelectedValueProperty

[RonPeters]

Let's say I want to build an app theme selector. I have the following page:

public SettingsPage(SettingsPageViewModel viewModel)
{
    BindingContext = viewModel;

    Content = new VerticalStackLayout
    {
        Children = {
            new Label { Text = "Theme" },
            new VerticalStackLayout
            {
                Children = {                        
                    new RadioButton { Content = "System default", Value = AppTheme.Unspecified  },
                    new RadioButton { Content = "Light", Value = AppTheme.Light },
                    new RadioButton { Content = "Dark", Value = AppTheme.Dark },
                }
            }
            .Bind(RadioButtonGroup.GroupNameProperty, "DesiredTheme")
            .Bind(RadioButtonGroup.SelectedValueProperty, static (SettingsPageViewModel vm) => vm.DesiredAppTheme, static (SettingsPageViewModel vm, AppTheme appTheme) => vm.DesiredAppTheme = appTheme),
        }
    };
}

The SelectedValueProperty is never bound in either direction. What is the proper syntax for this use case?

[h0lg]

I'm running into the same issue with a nullable enum property. Not sure if this is related to Maui.Markup, to MAUI itself or enum properties.
Is there a working solution or recommendation out there?