[rokweom]

With proper dithering, I would guess even rec. 2020 would be doable.

[meindnoch]

But that's cheating. You're effectively using N-times 8bit, by using N 8bit pixels to encode the intermediate values.

[rokweom]

If we consider dithering cheating, then 10 bit without dither is also not enough for banding-free 4K, no matter the color space.