I don't believe this will work with a single computer. If your graphics card dithers, it will do so regardless of the input source. Maybe streaming a bad pc to a good one could work.
Further, I had this hypothesis that some software I using was dithering and causing me discomfort. My daily pc uses a GTX660 graphic card which dithers, however it does not cause me discomfort, I believe I have adapted to it over the 7 years I've owned it. Some software causes me discomfort when using this PC.
My office PC uses intel integrated graphics (i5 6500, HD520) and does not dither. Because the graphics does not dither by default I've been using it to try to test for dithering in software. I can only test for the presence of dithering, not the type or origin, therefore I need a dither-free pc to test software. I have not been able to find any software dithering using this pc, also, software which strains me on my daily pc does not strain me on this. But I have not concluded testing yet. I believe that software has to ask the graphics card to dither, and maybe specifies the dithering function, but for whatever reason my desktop i5 6500 HD520 refuses to dither. I know it can dither, as I can turn it on. It might be because I had ditherig.exe turn dithering off when I did my last testing, and this is perhaps overriding any software request. Further testing needed.