ryujinx/Ryujinx.Ava/App.axaml

<Application
    x:Class="Ryujinx.Ava.App"
    xmlns="https://github.com/avaloniaui"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:sty="using:FluentAvalonia.Styling">
    <Application.Styles>
        <sty:FluentAvaloniaTheme UseSystemThemeOnWindows="False" />
    </Application.Styles>
</Application>