I'm setting up ditherig.exe on a PC for the first time myself and here's what I just did:
I downloaded the black-to-white grayscale image from here to use to test the dithering:
Interestingly, I found that either on the website in Firefox or when I made it my desktop image, the image would visibly waver upon scrolling it or upon moving a window over the desktop. The image would settle into a visibly static form after a few seconds, but it was really disturbing when wavering. It was making me sick and I couldn't initially find ditherig settings that completely eliminated the effect. It seemed like there was a bad Windows 10 effect going on in addition to or that was overriding ditherig.
I'm a novice to PCs (trying to switch from Macs since their screens are so bad), so I'm guessing someone else already mentioned this or would likely have known it's something obvious to do, but it was new to me - I found that I needed to follow the directions here to fully disable all of the Windows 10 visual effects through the Advanced System Properties menu. I thought I had previously turned visual effects off through the normal Settings menu options, but that hadn't been good enough.
After doing this, if I set the ditherig algorithm to "Spatial (default)," the grayscale image seems pretty stable. If the ditherig algorithm is set to "Disable all dithering functions (better resolution)" it's terrible -there's the visible fluctuation in the image - that setting must turn the ditherig program off, leaving pixel dithering on.
Maybe there's even better settings for ditherig, but I think the grayscale image linked above is a good test image for trying to figure it out.
I have an Acer Nitro 5, Intel UHD Graphics 630 (Coffee Lake), Windows 10 Home 20H2 - I got this laptop because it also has an Nvidia Geforce GTX driver and that is very helpful when using an external display. I'm now trying to make things good enough on the laptop monitor which uses the Intel GPU.