The Scene Color node returns a brighter scene color, and can therefore not create materials that are truly transparent, they will always have a tint. For most use cases this can be countered by applying a brightness tweak to the output, but gets more complicated when you have a dynamic scene with changing lighting.
Have tried both the HD Scene Color node and the regular Color Node, before and after post processing etc.Have tried multiplying with exposure.
I’m in HDRP with forward rendering.
Edit: it works in a completely empty scene, it is only when switching on Gradient Sky in the Post Processing volume that it stops working.
Edit: to those coming from Google - experiment with your Post Processing volume. Test to see which effects you can live without. In my case I need to switch off either the Gradient sky or parts of the fog in order for it to work.