Dithering is still needed for most of sRGBs range, Frontier needed to do it in Elite Dangerous where banding was noticeable. This paper: https://www.cl.cam.ac.uk/~rkm38/pdfs/boitard14hdr_colorspace... compares the bit depth necessary for contouring due to quantisation to become imperceptible across a few encodings, most of them in the 10-11 bits per channel area.