Draw Post Process Material to Render Target cannot use SceneTexture.
Found in 4.20 CL# 4369336, 4.21 CL# 4753647, 4.22 CL# 7053642, 4.23 CL# 7062535
The Render Target is completely black, nothing is written to the render target. Setting texCoord to emissive works as expected, the render target has the standard red/green UV gradient written to it.
The "Draw Material to Render Target" node should write the scenetextures to the render target. Even if the result is delayed by a frame.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-76604 in the post.