K-Moss
That is something I have wondered a lot.
I get migraines from IPS panels, flickering backlights, e-ink displays if they are displaying movement (static text is ok), and OLEDs. Some TN panels are ok, others are not. I've explored colour spectrum, polarisation and found they are aggravating factors but they are not the cause. I suspect VA is ok, but I can't be sure as I've never knowingly used a VA panel, but TVs are commonly VA and often they are ok. I believe my issues are primarily flickering and dithering, which I regard as related.
TN panels are broadly ok, but sometimes dithering can cause mild eye pain, and very rarely a migraine.
E-ink panels are very imprecise, if you see one displaying a movement of any kind it can appear very fuzzy, which in my opinion affects me the same as dithering - but only when its moving, e-ink does not bother me if it is displaying a static image, fuzzy or not.
Oleds flicker every frame when the pixels are updated.
LCDs of all kinds flicker, each pixel must be driven by an AC current as DC damages the liquid crystals. This means an LCD pixel is always flicking between light and dark, but because the AC voltage change is rapid and liquid crystals are slow to respond the effect is slight, and only noticeable if the voltages are wrong (called pixel walk / inversion I think).
I believe my migraines are triggered by my brain struggling to turn the flickering images my eyes are seeing into something coherent and clear. Paradoxically, of all the display types, IPS causes the most severe migraines, but IPS screens appear more stable to me than any other. Of the other bad display types, E-ink triggers the least severe migraines, but looks visibly fuzzy. The TN panel I am typing this with looks extremely fuzzy to my eyes but does not cause me discomfort.
So the conclusion I have come to is that my problems are caused by visual processing in my brain. Extremely fuzzy/heavily dithered TN panels are fine for me, because my brain doesn't even seem try to turn them into a smooth image inside my head, presumably because what I see is fuzzy enough that my brain believes it is supposed to be fuzzy and therefore does not process out the fuzziness. IPS on the other hand looks perfectly clear to me, I know it is flickering though because that's inherent to LCDs, so I presume my brain is processing out all the flicker/fuzziness of the IPS panel and thus triggering the most severe migraine.
So to summarise, flickering/dithering/fuzziness I can see is often OK, like my TN panel. flickering/dithering/fuzziness I can't see often causes me migraines, like IPS, backlight flicker, OLEDs flickering. E-ink is a bit odd in that I can see how fuzzy it is, but it only causes me very mild migraines. One day I hope to capture these effects on a high speed camera so I can confirm my hypothesis.
I am no longer searching for a hardware solution to these migraines. The problem is within me, and most likely my brain. I know from past experiences that my screen induced migraines can be entirely prevented with diet and supplements (its complicated, not something others can replicate unfortunately, and very bad for my health). Right now I am searching for drugs and supplements I can take long term without harming my body or brain.