Since Harrison mentioned me, I thought I would give an update on my situation.
I'm using my plasma TV as a my primary display now. It saved me. I can use it for hours when it is hooked up to an Nvidia GPU. At first I was getting eye strain while looking at the plasma, but I think it was because my eyes were already weakened by other displays. Once my eyes were rested after several weeks of only using the plasma I felt so much better. A lot of my chronic upper body pain was reduced significantly. I think the bad displays make my muscles tense badly. To make the plasma comfortable for long periods it is essential that I use dark themes in Windows and browser extensions to invert color (I am using Dark Reader on Chrome, it works better than some other extensions I tried, like Deluminate and the official High Contrast). Plasma's produce true blacks.
I can now look at some faulty displays for a short period without inducing the eyestrain/migraine/partial-seizure-like symptoms.
The EW2440L is a good monitor. I agree that it is a huge advantage that it can be very dim. It has developed some flickering which is very obvious and clearly not intended or PWM. I think the power supply has probably become faulty.
These are the displays I use now:
Primary - Panasonic plasma with Nvidia GPU
Secondary - BenQ EW2440L with Nvidia GPU
Secondary - old dell CCFL model (on full brightness, which causes the monitor to pass the blur trail PWM test) with Nvidia GPU. I use the OSD contrast setting and flux to tone down the brightness.
Out of necessity I use an HP ZR2740w with Intel iGPU. HP ZR2740w was one of the early LED monitors tested (by prad.de) to not use PWM. If my eyes are rested I can use it for a short while. Of course the Intel graphics introduces temporal dithering which I am sensitive to and the panel probably uses FRC to achieve 10-bit.