Computer Configuration > Administrative Templates > Citrix Components > Citrix Workspace > User experience
Machine
HKLM\Software\Policies\Citrix\ICA Client\Graphics Engine
Use this policy to enable or disable the use of H265 decoding for remote graphics. When not configured the use of H265 decoding is not attempted.When enabled, Citrix Workspace will attempt to use the client GPU to decode using H265 decoder as long the as server supports H265 encoding. On client devices that do not support this feature it is disabled silently and reverts back to H264