Here are some things you can try:
- Set lighting Technology to Future
- Set Ambient to [0, 0, 0]
- Make sure GlobalShadows is set to True
If these don’t work fully for you, you can also try:
- Setting Brightness to 0
- Setting TimeOfDay to 00:00
- Setting OutdoorAmbient to [0, 0, 0]
- Set EnvironmentDiffuseScale and EnvironmentSpecularScale to 1 (This won’t darken the room, see this post for more details)
Doing these will also affect other areas beyond indoor spaces.
If you need lighting to change based on different rooms/areas rather than simply whether or not the room is indoors, you will need to use something like ZonePlus for that.
(sorry for any errors and/or bad formatting, it is currently 6am and i haven’t slept yet)