Vividblu99 Yea I think you are on to something. As sometimes even when I use a phone that seem to have checked all the boxes I have listed above (for a comfortable experience), I still felt uncomfortable with only limited minutes of usage. I think there are other factors we have yet to identify that may be causing strain/ discomfort. I guess you are right about the gamma and the color temperature thing. Indeed it appears that it affects people differently.
Gosh, I am currently looking at three devices at the moment. It's either the Huawei Nova 9SE(non 5g edition. The 5g edition seems to be using a different LCD panel IMO), Iqoo Z7(China edition - LCD) and the moto G73. I have really high hopes for the G73 because it looks to be my perfect upgrade from the iphone 7 plus. However, as I spent most of my time reading on my smartphone,it will be a concern for me if there is discomfort in readability!
I know some website reports device screen as PWM free but when I bought the device and return back home I immediate got a dry eye from using it. I later read that the editor clarified that occasionally, they did not disclose their findings with lower brightness flickering because they felt the flickering is high enough that it will not bother most people anymore (probably over 2000~3000hz). Thus I'll wait for NBcheck report, and then see it in person again.
Hmm it's the first I have read about the possibility of protective glass causing eye strain. I do have read quite some time ago — about the gap between the touch screen glass panel and internal display. If the lcd display is not designed properly, the gap between will be wide till light will bounce around and reflect against both surface inside, resulting in glare when we see the display.
I'm still on the lookout to replace my smartphone. I was waiting for the rumored iphone se plus for years and apparently based on lastest report it was cancelled. Gone were the days where I never had to be constantly concerned about eye strains/ headaches.