2.2-AreaHunters/YJMPD-UWP/Themes/DarkTheme.xaml

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:YJMPD_UWP.Themes">

    <Style TargetType="RelativePanel" x:Key="DarkModeFix">
        <Setter Property="Background" Value="{ThemeResource SystemControlBackgroundChromeMediumLowBrush}" />
    </Style>

</ResourceDictionary>