Abuse display buffer to store upscaled image and blit it to the camera output destination in OnRenderImage. Bit of a hack but it works to support not outputting directly to the camera target.

Packages/com.unity.postprocessing@3.2.2/PostProcessing/Runtime/PostProcessLayer.cs

@@ -210,6 +210,7 @@ namespace UnityEngine.Rendering.PostProcessing
         CommandBuffer m_LegacyCmdBufferBeforeLighting;
         CommandBuffer m_LegacyCmdBufferOpaque;
         CommandBuffer m_LegacyCmdBuffer;
+        CommandBuffer m_BlitCmdBuffer;
         Camera m_Camera;
         PostProcessRenderContext m_CurrentContext;
         LogHistogram m_LogHistogram;
@@ -251,6 +252,7 @@ namespace UnityEngine.Rendering.PostProcessing
             m_LegacyCmdBufferBeforeLighting = new CommandBuffer { name = "Deferred Ambient Occlusion" };
             m_LegacyCmdBufferOpaque = new CommandBuffer { name = "Opaque Only Post-processing" };
             m_LegacyCmdBuffer = new CommandBuffer { name = "Post-processing" };
+            m_BlitCmdBuffer = new CommandBuffer { name = "Backbuffer blit" };
 
             m_Camera = GetComponent<Camera>();
 
@@ -281,6 +283,16 @@ namespace UnityEngine.Rendering.PostProcessing
         [ImageEffectUsesCommandBuffer]
         void OnRenderImage(RenderTexture src, RenderTexture dst)
         {
+            if (!finalBlitToCameraTarget && m_CurrentContext.IsSuperResolutionActive())
+            {
+                // Blit the upscaled image to the backbuffer
+                m_BlitCmdBuffer.Blit(m_CurrentContext.destination, dst);
+                Graphics.ExecuteCommandBuffer(m_BlitCmdBuffer);
+
+                RenderTexture.active = dst;
+                return;
+            }
+            
             if (finalBlitToCameraTarget && !m_CurrentContext.stereoActive && DynamicResolutionAllowsFinalBlitToCameraTarget())
                 RenderTexture.active = dst; // silence warning
             else
@@ -572,6 +584,7 @@ namespace UnityEngine.Rendering.PostProcessing
             m_LegacyCmdBufferBeforeLighting.Clear();
             m_LegacyCmdBufferOpaque.Clear();
             m_LegacyCmdBuffer.Clear();
+            m_BlitCmdBuffer.Clear();
 
             SetupContext(context);
             
@@ -627,7 +640,7 @@ namespace UnityEngine.Rendering.PostProcessing
             bool isFogActive = fog.IsEnabledAndSupported(context);
             bool hasCustomOpaqueOnlyEffects = HasOpaqueOnlyEffects(context);
             int opaqueOnlyEffects = 0;
-            // TODO: if FSR2 is active, add opaque-only copy step
+            // TODO: if FSR2 is active & using auto-reactive/TCR, add opaque-only copy step
             opaqueOnlyEffects += isScreenSpaceReflectionsActive ? 1 : 0;
             opaqueOnlyEffects += isFogActive ? 1 : 0;
             opaqueOnlyEffects += hasCustomOpaqueOnlyEffects ? 1 : 0;
@@ -701,6 +714,13 @@ namespace UnityEngine.Rendering.PostProcessing
 
             context.destination = cameraTarget;
 
+            if (!finalBlitToCameraTarget && m_CurrentContext.IsSuperResolutionActive())
+            {
+                // Use the main display buffer for temporarily storing the upscaled full-resolution image
+                context.flip = true;
+                context.destination = Display.main.colorBuffer;
+            }
+
 #if UNITY_2019_1_OR_NEWER
             if (finalBlitToCameraTarget && !m_CurrentContext.stereoActive && !RuntimeUtilities.scriptableRenderPipelineActive && DynamicResolutionAllowsFinalBlitToCameraTarget())
             {