Tested on 2021.1.0a6 + HDRP 10.1

Steps to repro:

1) Start a new HDRP project (make a template or just import package)
2) Create a new Render Texture
3) Try selecting the sRGB option for color format (the first in the list)
4) Observe it resets to UNORM all the time

Expected behavior: Even though HDRP works in linear space sRGB target texture will still be converted so it should be selectable.