presence/Presence.Desktop/App.axaml

<Application xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="Presence.Desktop.App"
             RequestedThemeVariant="Default">
    <!-- "Default" ThemeVariant follows system theme variant. "Dark" or "Light" are other available options. -->
    <Application.Styles>
        <StyleInclude Source="avares://Avalonia.Controls.DataGrid/Themes/Fluent.xaml"/>
        <FluentTheme />
    </Application.Styles>
</Application>