var notification = new NotificationRequest
{
    NotificationId = 100,
    Title = "Test",
    Description = "Test Description",
    //If not specified, the default sound will be played. In Android, this must be set at the channel level for new versions of Android. 
    Sound = DeviceInfo.Platform == DevicePlatform.Android ?  "<file name without extension>" : "file name with extension", 
};
LocalNotificationCenter.Current.Show(notification);

public static class MauiProgram
{
	public static MauiApp CreateMauiApp()
	{
		var builder = MauiApp.CreateBuilder();
		builder
			.UseMauiApp<App>()
			....
			.UseLocalNotification(config =>
			{
                                config.AddAndroid(android =>
				{
					android.AddChannel(new NotificationChannelRequest
					{
						Sound = "good_things_happen"
					});
				});
			});
               return builder.Build();
	}
}

public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
{
	protected override void OnCreate(Bundle savedInstanceState)
	{
                .....
                // Must create a Notification Channel when API >= 26
                // you can create multiple Notification Channels with different names.
                LocalNotificationCenter.CreateNotificationChannel(
                        new Plugin.LocalNotification.Platform.Droid.NotificationChannelRequest
                        {
                                Sound = Resource.Raw.<file name without extension>.ToString()
                        });
		.....	
                LoadApplication(new App());
		.....	
		LocalNotificationCenter.NotifyNotificationTapped(Intent);
	}

	protected override void OnNewIntent(Intent intent)
	{
		LocalNotificationCenter.NotifyNotificationTapped(intent);
		base.OnNewIntent(intent);
	}
}