Hey!
Network, it was supposed to be yes! And some things would be definitely hardwired...
I think it’s blue concrete? That nasty stuff you can carve out with a knife, really porous and unpleasant.
Any tips on suitable filler to patch these up with? Does gypsum mortar work, for example? The wall will probably get a round of fiberglass-reinforced wallpaper due to general disrepair, so I'm not too worried about cracks, etc.