With reference to https://learn.microsoft.com/en-us/dotnet/maui/fundamentals/shell/navigation?view=net-maui-8.0 I see that the IconOverride takes an ImageSource parameter, hence, a FontImageSource.

However, how is it possible to set this FontImageSource through XAML?

<ContentPage ...>    
    <Shell.BackButtonBehavior>
        <BackButtonBehavior Command="{Binding BackCommand}"
                            IconOverride="back.png" />   
    </Shell.BackButtonBehavior>
    ...
</ContentPage>

Thanks a lot!