There is no ListBox.SelectionMode="None", is there another way to disable selection in a listbox?

Approach 1 - ItemsControl

Unless you need other aspects of the ListBox, you could use ItemsControl instead. It places items in the ItemsPanel and doesn't have the concept of selection.

<ItemsControl ItemsSource="{Binding MyItems}" />

By default, ItemsControl doesn't support virtualization of its child elements. If you have a lot of items, virtualization can reduce memory usage and improve performance, in which case you could use approach 2 and style the ListBox, or add virtualisation to your ItemsControl.

Approach 2 - Styling ListBox

Alternatively, just style the ListBox such that the selection is not visible.

<ListBox.Resources>
  <Style TargetType="ListBoxItem">
    <Style.Resources>
      <!-- SelectedItem with focus -->
      <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}"
                       Color="Transparent" />
      <!-- SelectedItem without focus -->
      <SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}"
                       Color="Transparent" />
      <!-- SelectedItem text foreground -->
      <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}"
                       Color="Black" />
    </Style.Resources>
    <Setter Property="FocusVisualStyle" Value="{x:Null}" />
  </Style>
</ListBox.Resources>

I found a very simple and straight forward solution working for me, I hope it would do for you as well

<ListBox ItemsSource="{Items}">
    <ListBox.ItemContainerStyle>
       <Style TargetType="{x:Type ListBoxItem}">
           <Setter Property="Focusable" Value="False"/>
       </Style>
    </ListBox.ItemContainerStyle>
</ListBox>

You could switch to using an ItemsControl instead of a ListBox. An ItemsControl has no concept of selection, so there's nothing to turn off.