degen I can only speak from personal experience. Reflection/intensity of the light is a big variable (or has been for me)
In my back basement, I installed some overhead florescent lighting. 0 issues, I am down there for hours and hours at a time. We have the basement waterproofed, and they added a reflective white plastic material on the walls. The room now instantly gave me a migraine. I cut the plastic down, and the problem vanished. No change to the lighting, the light bulbs, or anything in the environment, just the amount of reflected light that hit my eye
In my front basement I have LED bulbs that cause me no issues whatsoever. I installed the same bulbs in the lights in the gaming area of my front basement, where the drop ceiling is 1 inch lower. That 1 inch of difference, coupled with being closer to the walls and resulting in more light reflectivity, causes me instant symptoms. Thats with the same bulb, the same fixture, the same ceiling, I even wired the whole lighting setup myself so I know even the wiring is identical.
Recently installed overhead lights in my family room, I put in incandescent bulbs which to date have never cause me an issue. Instantly triggered my migraines. The room has a very waxed floor, and the walls are painted yellow. The same exact bulbs (like, I unscrewed them and moved them myself) in a standing floor lamp in the same room? ZERO issues. Put that same bulb in an overhead lamp? Instantly unusable.
I have also inadvertently rendered computer monitors unusable by painting the room itself. I had a Sony monitor in my old office that was panted a light blue, used it all day, every day, with no issues.Painted the room green, the monitor was completely unusable and I had to sell it.
This dovetails into my theory that color of light has a major impact on our condition. Different wavelengths of light effect us, and the intensity of those wavelengths, and when a combination of a particular color and intensity of that color hits our eye, it triggers our brain to misinterpret the visual input and go haywire, resulting in symptoms.
For me at least this hypothesis holds far more water than flicker or PWM or dithering. I know a lot of people are really hooked on those theories, but they just seem a little convenient as scapegoats. I think the folks who found relief by eliminating flicker or PWM were actually getting relief by reducing light intensity and that is what is going on, but again thats just a hypothesis, I cant prove it