Sorry, been travelling, so away from the forum... So, I took a closer look and see that, yes, it's just a dummy - a black plastic molding with a silver-painted "U" trim ring. I assume it's just for appearance's sake, but they could've just put a marker LED in there (like the CX-5 has). I thought I might modify it to insert a switchback DRL light, but looking at the shop manual, you have to remove the front bumper to get at the light assemblies and then retrain the camera and forward radar when you put the bumper back. Ugh. I've had the bumper off my CX-5 and that was relatively easy, but not this car
So, I'll probably just leave it be.