Fiber 100 Setup with personal router

Last known AT&T Gateways (modem/router combo units) are proprietary and you cannot use a 3rd party box to receive the service. Though you can use an additional router or such that receives the service from the Gateway if you need to further manage the home network.

Use the gateway att requires you to use and see how it works for you. Depending on your home size and layout, you may not need an additional router. 

Thanks for the above, but ATT had no issue with me using my own, so I don't believe the first answer is accurate. As for the second answer, this is exactly the solution I am trying to avoid as noted in the question. Other thoughts welcome.

You have to use the att gateway provided. Unless you want to try and bypass the required gateway. I’ll let you google that.

You can use a third party router or mesh WiFi system behind the att gateway.  

@Solar_Wind 

Thanks for the above, but ATT had no issue with me using my own, so I don't believe the first answer is accurate. As for the second answer, this is exactly the solution I am trying to avoid as noted in the question. Other thoughts welcome.

No AT&T has no trouble with you using your own secondary router.

However for Fiber service you will receive an AT&T Modem with an integrated ONT or with an external ONT. And you will be paying $10 per month for the equipment fee.

Now with that as a base level. You have a couple of options.

1. Add your secondary router behind the AT&T Gateway in IP/Passthrough mode
2. Try a bypass method to use your router as the primary router. there are a couple of methods. This will not work if your area has been upgraded to XGS-PON
   

However if you get the new BGW320 Gateway from AT&T with the integrated ONT active there is no known way to bypass at this time. You will have to use IP/Passthrough mode.

Dave