If you are willing to move to Ubiquiti hardware (recommended, security breach from today notwithstanding) there's a relatively straightforward bypass method where the authentication packets are forwarded from the ONT to the AT&T box but it's otherwise out of the loop, and you have fully native routing with the Ubiquiti USG (a really nice router and ecosystem).
Instructions: https://medium.com/@mrtcve/at-t-gigabit-fiber-modem-bypass-u... Github project that makes it possible: https://github.com/jaysoffian/eap_proxy
It's definitely not plug and play but I've been using this setup for a year and a half and I get my full 1gb bandwidth throughout my network with lots of hosts.
Re:My ISP Is Killing My Idle SSH Sessions
by lights0123 on Tuesday January 12, 2021 @11:06AM
(#25748692)
AT&T has started using a much newer gateway for new installations.
Re:My ISP Is Killing My Idle SSH Sessions
by diegs on Wednesday January 13, 2021 @12:18AM
(#25758498)
Damn, that's a serious bummer. I hope mine doesn't break anytime soon.
If you have the BGW210 gateway there is a written series of steps for root here:
https://github.com/Archerious/bgw210-root
As well as step by step configuration for complete gateway bypass on Mikrotik router hardware here:
https://forum.mikrotik.com/viewtopic.php?t=154954
If you are stuck with the newer XG-PON hardware, it looks like you might be out of luck for now.
I didn't know their box even had certs, or what "ONT" is. Is there like... a written series of steps I could follow?