You don’t need privileged. If you look at the official thread on privileged lxc (PROXMOX), you will see my comment explaining how to make it work unprivileged. It’s pretty simple - only a couple changes from the instructions. I can’t advise for TrueNAS (I don’t use it). But my solution works fine for proxmox unprivileged lxc and I’ve been using it since the day I made that comment.