Theres messages that need descyphering in the darkness, you can't see them normally and have to use your flashlight or spawn a light source to get them visible.

To navigate around in the dark easier you can use Fog Editor entity and set fog start to 0 and fog end to 100 to take a closer look, a 1000 to navigate around the debris, and up to 5000 to be able to see the entirety of available area around.

Good luck, so far found about 1 message in every big debri pile, painted either on the wall or on the "flooring". Also theres a QR code in the same debri that looks like a "runway" for aircraft, but ends with a 90 degrees turn and several columns. Painted on the side of that runway near one of the columns.