I'm in the same boat. It is just too bright in the dark.
My guess is that the hardware that DUDU has is not capable to go lower in brightness and that is why they did the "Extreme dark" option as a workaround. If I'm right, which I hope I'm not, this will never be solved.

I am on the same boat too.
I was thinking of cutting a tinting film to the shape of the screen and apply it on the screen. A kind of natural ND filter.

It will mess with the colors of the screen and with the peak brightness too. Not a very elegant solution.

a month later

Please address this issue, the radio is really annoying after dark.

It is possible to set saturation, brightness and color when in reverse gear settings.
Maybe this could also work for normal use?