The utility logmix (ucyblgmx) is missing in the image for 21.0. It was available in previous versions.
Release : 21.0.3
Component : AUTOMATION ENGINE
This is by design and a decision that was made by Broadcom to remove the logmix tool as it is meant for internal use only
AE.LogMix has been officially removed from all packages and images 21.0.3 and later
It has also been removed from the v21 utilities product documentation.
Previous versions can still be used if needed until they are no longer available, but there is no guarantee they will work as this is not a maintained component.