I’ve also come across this video:
https://youtu.be/tvo5QcMs4uc?t=4193
With this it seems that metallic is working with Dbuffer decals as well as a way to have POM using UE4 decal domain and blend modes, which if I understood correctly from the other threads about this issues, wasn’t supposed to be working in UE4? I feel like I’m missing/not getting something.
The documentation also specifically states the DBuffer blending modes are non-metallic, yet the pin in the shader isn’t greyed out when switching to those blending modes.
Still hoping for some details from @JamesCLight 