Heya, working on a modpack which has both the Erebus and Harcore Darkness, I have not added any dimensions to the Hardcore Darkness Blacklist so it should make the Erebus dark, but it doesn't work at all. No clue if that's caused by the Erebus or Hardcore Darkness, but it seems like Lumien isn't doing anything on HD anymore so maybe better to ask here?

Any update on this?

Nope.

Are you using Phosphor?
Phosphor and HD don't work togheter, Phosphor also breaks Dynamic Lights unfortunately.

I have no idea what Phosphor is so most likely not using it. Hardcore Darkness does work in other Dimensions too.