installing a package as nonroot

[circumspect.readabilities830 at aceecat.org]

First, I installed texlive 2023 with the network installer into
/opt/texlive/2023 (choosing the tetex profile).

Then I did something like the following (itz is my login name):

  groupadd texlive
  chgrp -R texlive /opt/texlive/
  find /opt/texlive -type d -exec chmod 2775 {} +
  adduser itz texlive

Lastly, I tried to run

  tlmgr install latexmk

while logged in as myself (and yes I did log out and back in after
adding myself to the group). This last command fails due to ENOPERM.
How so?

-- 
Ian