I have a project where I'm playing with a video feedback effect by rendering a camera to a RenderTexture and pointing the camera at a quad displaying that RenderTexture.
This works great normally, but when trying out HDRP, LWRP, (and upgrading materials) or upgrading the entire project to 2018.3, the RenderTexture just stops working and shows black. I also tried with a completely new project and just had a camera, a quad, and a cube. That also didn't work.
Is there any obvious reason this wouldn't be working? I spent a while trying out various settings but couldn't find anything that had any effect, so I really don't even know where to start.