In my case 19.10.1 (I think it was) fixed it originally, 19.12.2/3 aka Adrenalin 2020 broke again and now Adrenalin 2020 20.1.1 fixed it again.
Sapphire RX 5700 XT Pulse + Samsung C32HG70
All those overlay etc stuff couple posts above has never been the issue in my case.
a number of drivers has been released but no improvement of hdr color in youtube video and gaming for 5700xt. Totally washed out. Really disappointing. Finally it seems to me 5700xt hdr is broken !
Its still broken on my Nitro+ 5700XT and Samsung C27HG70... Washed out, or too bright....
Latest drivers 20.3.1
(clean install windows and all updates and new drivers as well as latest FW)