AT&T Pace 5268ac Step-by-Step

After reviewing the community posts, the Netgear instructions for the Orbi, and called Netgear, I still have question on setting up an Orbi behind an AT&T Pace 5268ac UVerse Gateway (no VOIP -- at present -- and no TV).  AT&T will not provide any assistance on the best configuration to setup Pace device in a way to approximate a bridge mode, which doe snot technically exist on the Pace gateway.  The Internet abounds with workarounds.  Netgear will not give that advice on how to configure in the Pace menu.  If you want to use the Orbi as the router (equivalent to bridge mode) and not as a repeater/extender, what are the best step-by-step instructions for BOTH devices (Pace and Orbi).  There is no such formal documentation.  On the Pace it seems that it is some combination of turning off wi-fi, putt notice on related to router behind router configuration, and setting up a DMZ for the Orbi -- not exactly plug and play.