The code is much simple.
The page defined as following
<Page
x:Class="UwpApp1.Gallery"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:UwpApp1"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
Width="500">
<GridView x:Name="CoverArtsTable"
Grid.Row="1"
ItemsSource="{x:Bind CoverArts}"
IsItemClickEnabled="True"
ItemClick="CoverArtsTable_ItemClick"
SelectionMode="Single"
IsSynchronizedWithCurrentItem ="False"
Margin="0 5 0 0">
<GridView.ItemContainerStyle>
<Style TargetType="GridViewItem">
<Setter Property="Margin" Value="0,0,10,10"/>
</Style>
</GridView.ItemContainerStyle>
<GridView.ItemTemplate>
<DataTemplate x:DataType="x:String">
<Frame CornerRadius="5" Padding="0">
<Grid
Width="155"
Height="242"
Background="DimGray">
<Image
Name="CoverArtImage"
AutomationProperties.AccessibilityView="Raw"
Stretch="Fill"
Source="{Binding}" />
</Grid>
</Frame>
</DataTemplate>
</GridView.ItemTemplate>
</GridView>
</Page>
The ContentDialog opened by this way
var dialog = new ContentDialog();
var page = new Gallery();
dialog.Content = page;
dialog.Title = "Test";
dialog.CloseButtonText = "Cancel";
dialog.DefaultButton = ContentDialogButton.Primary;
dialog.PrimaryButtonText = "Save";
dialog.PrimaryButtonClick += (s, a) =>{};
await dialog.ShowAsync();
No frame on Win11 at item selection.