karut Well, then you can try ATI 6bit. Use the AMD Pro drivers instead of adrenalin drivers. (see post above)
If you want to play video games on 1080p 6600xt is ok, i can play cyberpunk on medium details, Witcher3 & Borderlands 3 on high-highest. Will be ok for the next 4 years i think. If you are using more than 1080p think about a higher think about the 6700xt or 6800xt. Just saying 
I wanted to try my wifes Macbook, but hadnt the time for it till now.
So basically, to change the AMD GPU output color depth ( to 6 bit in my case ) , we need to connect via Display Port or HDMI is working too?
Allekss No, it only works with an DP-cable. No idea why.
I downloaded AMD Pro Driver fro my 6500XT ( connected to Monitor via HDMI ) and I'm able to change Color Depth 8, 10 or 12 ( photo 1 ).
Also, I'm able to change Full RGB ( default settings ) to Limited RGB !!! What a big difference ( photo 2 & 3 ).
Are you able to use 6bit colors? I have tried it with 3 monitors, always worked with a DP-cable, never with a HDMI-cable
hayder1983 No , i don't have that option 
min for me is 8 bit via HDMI. Need and DP to try it ( my monitor also doesn't have DP port :// )
Allekss #OK. Dont buy an adapter cable, it wont give you the option. Tried it with DP-to-DVI, doesnt work, it display DVI as connection, see below.
hayder1983 Do you feel well with it?
hayder1983 i have to test it for a week or two. If it doesn't work, i assume it is a body/physical issue for me!!
Should your problem not go away, send your card back and try glasses and eyedrops/healing ointment. It helped me reduce eye strain a lot. Dithering is still a problem for me, watching TV is still straining to me, but using the PC is much better now. I just have 0,75 dioptrin on each eye, still made a huge difference.
You could also try lenses, because it would be cheaper to try. They cost like under 20$ for 30 lenses.
hayder1983 I've just tried to play with contrast both in adrenalin and monitor, look like vivid gaming doing something with gamma i guess, completly different results. I'm trying to adjust green, much green in some videos and artifacts on black shades.
WeinTrust i think it is much more contrast and different gamma, which will oversaturate a lot colors and change gamma for all colors. I cant find a sweet point that way.
I am pretty sure dithering is not off, even with 6bit colors. I can see the dithering on grey and white. Dont buy a new AMD card just to turn off dithering, it doesnt work. Sorry 
reaganry You are right. Look it does calmer to you?
The option right below(GPU-Skalierung, dont know the english name) seems to affect dither too, at least on my old LG. I am using it on native resolution. You can use them both at once. Not sure why this makes a difference, but it looks like it does.
I just changed the monitor driver for my super old LG monitor and i am using the "PnP-Monitor" now. It is different now, still dithering. AMD Pro driver still knows what monitor is connected.
I just tried using different color scheme on my browser with colors of the 6bit palette(see below). I have to test it a few days, so i dont imagine things…
https://lospec.com/palette-list/6-bit-rgb
I dont think anything in the settings of driver will really disable it. It seems dithering is everywhere. Steam deck is supposed to have no dithering at all(not sure) and it has windows emulated on it. I will try to plug it on an Monitor in a few days( not today, my brain is overheating) and see for my self. I could live with Steam deck+Monitor with integrated docking station as an Home PC. I have everything at home right now, just need the time to do it 
Just tried Super resolution and on the highest(!) resolution available(2,28xnative resolution). On similar scaling for some reason reading text is easier on the eyes. Not sure why, it is different kind of sharpness? If reading gets easier, eye sore should get bit less. Thanks for the suggestion
hayder1983 I have a dock for my steam deck but unfortunately at the current time I can only use hdmi with it, not displayport yet (waiting on an update, none of my dp adapters work with it). I do think I can see frc dithering on desktop mode, but the thing is, I'm using a monitor that ALREADY has frc dithering.. so I can't easily tell if it's both the panel and the driver at the same time or just one. I'm fine with the purchase, it isn't perfect but it is usable and I don't feel the need to get rid of it. Will be interesting to see what updates to it (kernel, driver, etc.) do.
I still prefer using my older PC as a desktop, I don't use the SD as a desktop even tho it's more powerful. I'll re-consider down the road when support for Windows dual-boot is better.