maui-linux/Xamarin.Forms.Platform.WPF/Themes/FormsSymbolIcon.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:controls="clr-namespace:Xamarin.Forms.Platform.WPF.Controls">
 
    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="/Xamarin.Forms.Platform.WPF;component/Assets/Converters.xaml" />
    </ResourceDictionary.MergedDictionaries>
    
    <Style TargetType="controls:FormsSymbolIcon">
        <Setter Property="HorizontalAlignment" Value="Stretch"/>
        <Setter Property="VerticalAlignment" Value="Stretch"/>
        <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
        <Setter Property="FontSize" Value="22"/>
        
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="controls:FormsSymbolIcon">
                    <TextBlock Text="{Binding Symbol, RelativeSource={RelativeSource Mode=TemplatedParent}, Converter={StaticResource SymbolToValue}}" 
                               FontSize="{TemplateBinding FontSize}" 
                               FontFamily="Segoe MDL2 Assets"
                               TextOptions.TextRenderingMode="Grayscale"/>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</ResourceDictionary>