Also, I understand the way they have the Debian configured/customized may have made a traditional authentication more difficult to implement in nginx (pure speculation on my part). From my router, to networked cameras, Raspberry Pis running Node-RED, OctoPrint, MotionEye, NAS... I can't think of a LAN'd thing I own that doesn't have some way of locking its front door.
I though about messing around with ufw, but I don't want to lock myself out!