Windows 10: cannot turn off adaptive contrast, even in registry or with command prompt

I just purchased a used Surface Pro 7, and have been trying for days to find a way to disable the adaptive contrast "feature". I've been all over the internet, attempting all sorts of solutions, but not one has done anything. From what I've gathered, the feature is meant to save battery power by detecting what's on screen, and changing the contrast level automatically. I use this device primarily at home, with an external display, so there's no need for this feature to be enabled. I don't frequently need to use it on battery power, and would use other methods to optimize battery life. The feat

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How to backup and restore registry using only win10 iso command prompt

In a link it suggested several registry troubleshooting steps for a Windows with black screen.

For Windows 10 1909 how do you backup and restore one registry change using a windows 10 iso command prompt?

If more than one registry entry is modified how do you backup and restore a second change?

In addition to modifying one or two commands how do you backup and restore the whole registry when the only access is via a windows 10 iso command prompt?

 

command prompt will not open in safe mode with command prompt

Would I just follow the same steps within safe mode after hooking up to the other system?

 

registry edit no longer controls adaptive contrast

i have a laptop running windows 10, and one of the most irritating "features" is adaptive contrast: if a website has a gray or dark background, the brightness will gradually dim. it gradually brightens if you switch to a white window or website.

it can be very difficult to find help with disabling this feature, because microsoft staff frequently confuse it with adaptive brightness, which relies on sensors to detect ambient light. adaptive brightness can be controlled through power settings. but
adaptive contrast cannot be directly controlled.

and every time windows forces me to update, it turns adaptive contrast back on. for the past couple of years, i have relied on a registry edit that adjusts the value of "featuretestcontrol" and, in the past, worked. loosely stated, i would edit the value
directly. however, this fix no longer seems to work. specifically, in the bit field for the featuretestcontrol key, changing the applicable bit to "1" used to turn contrast off, but i still get the problem even with the bit set to 1.

does anyone know a workaround? are we stuck with this eye-killing "feature"?