@ChuckPa and other Asustor’s owners 
I may have (with little help on another forum) find where is the problem, or was ! Because I now have my HW transcode back !
I have some more tests to run to be sure it’s finally working correctly with all types of medias.
So, where was the problem?
On the Asustor ADM side!
With a recent update of ADM, there is a new setting I totally didn’t see :
When I check this checkbox , and reboot as asked, the docker Plex installation can now transcode with the iGPU !
But I don’t know why the native Plex package installation with adm doesn’t works correctly with this option deactivated… as it is explain it should works without activating this… no?
I’ll get back to you after I ran some more tests.
But I think it’s working.
But there is a medium cpu usage while transcoding : about 35%. I think this is a bit too much for HW transcoding, but the 4k hdr transcoded is smooth.
