<telerik:RadButton x:Name="button" Text="hello telerik button">
                <telerik:RadButton.Background>
                    <LinearGradientBrush EndPoint="0,1">
                        <GradientStop Offset="0.0" Color="Violet" />
                        <GradientStop Offset="1.0" Color="DarkRed" />
                    </LinearGradientBrush>
                </telerik:RadButton.Background>
 </telerik:RadButton>

this.myButton.Text = "4" + Environment.NewLine + "Totals Files";

<telerik:RadButton Grid.Row="6" BackgroundImage="image.png" VerticalOptions="Center" HorizontalOptions="Center" WidthRequest="100" HeightRequest="100" Clicked="RadButton_Clicked"/>

private void RadButton_Clicked(object sender, EventArgs e)
{
	(sender as Telerik.Maui.Controls.RadButton).BackgroundImage = "image2.png";
}

<Style TargetType="telerik:RadButton" x:Key="MyTelerikButtonStyle">
            <Setter Property="TextColor" Value="{DynamicResource MyPrimaryColor}" />
            <Setter Property="BackgroundColor" Value="{DynamicResource MySecondaryColor}" />
            <Style.Triggers>
                <Trigger TargetType="telerik:RadButton" Property="IsEnabled" Value="false" >
                    <Setter Property="BackgroundColor" Value="Gray" />
                </Trigger>
            </Style.Triggers>
</Style>

 <Setter Property="TextColor" Value="White" />
 <Setter Property="BackgroundColor" Value="Green" />