This is problem on HP laptop which has 2 video controllers.
By using prime-select you can choose Intel or Nvidia.
If you choose "prime-select intel", then xgamma working, but you are using low speed video controller.
If you choose "prime-select nvidia" then xgamma not working, but you are using high speed.
On the same laptop in Windows even if you use Nvidia, you still can open Intel panel and change gamma settings separately.
Does anyone knows a way to fix configure gamma when prime profile is Nvidia?