Actually it can be done in the ENB too, but it would require some heavy overhauling of previous settings.
What about SweetFX dithering option does that work properly, I tried it myself but I couldn't see any better or worse on my end though I did not have any banding as I was using ELE, or EWE back when I tested it

To my latest ELE - Weather type SkyrimClearRE this is my coloring for the Day sky color, without any banding, a bit at the very top but it's few stripes that isn't that noticeable.
Horizon - 193, 216, 230
Sky Lower/Middle - 132, 170, 219
Sky Upper/Top - 98, 133, 187
It all comes down to finding the right color luminance between the three areas which blends together with as little banding as possible, a lot of trial & error in other words. Luckily I have taken some good reference pictures (actually 1000+ images with 5-10 sets of pictures per reference) that narrows down the Trial & Error run
