This cron job runs once a week on Wednesdays, deleting all artifacts in the toolforge project that are not within scope of toolforge_repo_artifact_limit as defined in the config.
It seems that non-admin users no longer have permissions to GET immutabletagrules (admin users still can). All other jobs seem to be able to run.
Upon further investigation, this seems to have been an artifact of my lima-kilo harbor instance, where I had a few test projects that weren't created/admin'd by maintain-harbor. I will do a bit more testing, but hopefully this turns out to be a non-issue.
Indeed, this seems to have been an issue only in (my particular setup of) lima-kilo. Sorry for the confusion! Non-admin permissions are not broken in Harbor 2.10. Closing this as invalid and moving on. I've tested maintain-harbor in production (!) and nothing breaks.