Phone support does not know what bring your own router is for fiber ONU

I am trying to use my own router with my fiber Internet and I have spoken to 3 different customer support agents who do not know what I am talking about. They keep trying to bridge my XER10 router which can not be done nor what I want . Any tips on what to do here? Or who to speak to?

https://www.xfinity.com/support/articles/member-owned-router-fiber-internet