Apologies if the question seemed offensive. I merely asked because after compiling your experimental branch and opening the example project (not the launcher one) I am greeted with this.
Having looked at your explanation of how the materials work, it seems correctly set-up by being default lit even though the custom data 0 and 1 pin are greyed out compared to your OP example.
Exploring the project file’s settings I realized that auto exposure was turned on, so I simply assumed that it was intended for use with post processing volumes.
In this case, my I ask you for possible reasons as to why the source example project isn’t working with the 5.4 experimental source build out of the box? I’d really like to experiment with your work.