A thread on the old Oxide site that I referenced weekly appears to have been killed sometime in the past 24 hours:

https://oxidemod.org/threads/using-the-oxide-permission-system.24291/

Does anyone know of another good reference or official docs for Oxide/UMOD permissions?

They've been on our site for a few months: https://umod.org/documentation/plugins/permissions

Thanks Wulf...don't know how I missed that, derp.

The docs probably aren't the easiest to navigate right now, so probably not on you. ;)