Try open the softrender mode tode debug the FramebufferRenderTarget

samples/RenderDemo/App.xaml.cs

@@ -1,6 +1,8 @@
 using Avalonia;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Markup.Xaml;
+using Avalonia.Media;
+using System.Collections.Generic;
 
 namespace RenderDemo
 {
@@ -29,6 +31,7 @@ namespace RenderDemo
                .With(new Win32PlatformOptions
                {
                    OverlayPopups = true,
+                   RenderingMode = new List<Win32RenderingMode>(){ Win32RenderingMode.Software }
                })
                 .UsePlatformDetect()
                 .LogToTrace();