Tom220 Very sorry to hear about your problems.
If I recall correctly, DELL XPS was judged one of the few completely eyestrain-free laptops by more than one user on this forum, at the point that I was considering getting one. Many people cannot instead use MacBooks later than 2015.
My conclusion is that there is no common denominator at all for our visual issues and no one really knows what is going on wrong. The individual may be lucky and skilled to find a good solution for himself, but this is almost never going to apply to another person. It is super demoralizing.
Sorry for sounding this negative. I know I have not answered your question. I guess no one can.