To add to what others have said: I’m using an Intel UHD 620 on Windows 11 (23H2), and toggling ditherig.exe technically works on my specific device and software combo. It clearly affects visual banding – easy to spot in videos, images, or Lagom.nl tests. But when it comes to major biological symptoms, I’ve noticed no real difference.
I’ve used this laptop for a few years without ever changing dithering settings. Now that I’ve disabled everything, there's still no clear improvement. Maybe there are small changes I just can’t detect. Subjectively, I think if you're not highly sensitive to dithering (e.g. not getting instant or quick nausea, migraines, vertigo), you might still get a slight reduction in general eye strain – possibly due to reduced flicker. That’s anecdotal, of course, and very hard to measure.
For reference, this is a G5 HP ProBook. I ran an interesting test: I swapped its panel into a newer G8 version with an Iris Xe GPU, same Windows version. With the Xe drivers and dithering off – I get immediate strong symptoms. Disabling dithering again made no noticable difference. But switching to the Windows Basic Display Driver made the laptop usable (as I understand ditherig.exe doesn't work on basic display driver as intel one is not used). There are still some adjustments I need to make biologically (not sure what exactly it is and why), but I can function on it pretty well. I don’t use it as my main portable device yet, since the Basic Driver kills battery life (2–3 hours vs ~8 with proper drivers). It's still a work in progress to see if I can 100% adapt (like I did to g5 probook) to this device on basic display driver.
So, ditherig.exe might help someone who's very sensitive to this particular dithering method which can be turned off with this specific software – but there’s much more to the picture than this program.