In my experience iPhone FaceID works fine at night, with brightness all the way down. It shines infrared at you (you can vaguely see some light red emitting from next to the camera, some bleed from the infrared) and then captures that with the camera. It might also use LiDAR, I’m not totally sure. It even unlocks while I’m wearing my CPAP, believe it or not, because since the updates to make it work with masks it pays more attention to the area around the eyes.