Ok, so one thing that would explain both the initial issue with raw.idmap and what you’re seeing now is if the directories within your tank/video dataset are also datasets.
If they are, then you need a separate disk device for each of them as they are separate mounts as far as Linux is concerned.
Of course, because they are mounted! I never thought about that. I’ll try to add them as well.
Both raw.idmap and shiftfs works for me. The problem was that the directory i mounted in the container only contained zfs datasets. Once those datasets were mounted as well, the expected owner and group were reported in the container as well.
Thank you very much for your help, and thank\s for showing me shiftfs.