I have a 9.36" DUDU7, same problem. It's unusable and dangerously blinding at night, especially considering there's no dark mode (???? seriously????) So you have a blinding, bright white screen that can't dim to a reasonable level, even by going into the android settings.
I bought the DUDU7 because supposedly the software is AMAZING and free of bugs. It's been a mess IMHO so far. The little robot assistant that calls me "Master" is creepy as hell. Fortunately I was able to turn him off. But no dark mode? No brightness adjustment? After a year or so of complaints? I'm going to have to return this and figure something else out, maybe go with an older 7862 unit.