I setup a mob farm with Mob Grinding Utils' Dreadful Dirt. No mobs are spawning.

I have night vision via EveryLastingAbilities, which is why it all seems lit up, but I disabled it then re-entered the Hyperbox, and it seemed plenty dark.

ATM9 To the Sky - 1.1.1

Hyperbox-1.20.1-4.0.2.0

The hyperbox biome intentionally has no mob spawn entries