Searching reveals much convoluted discussion about configuring pass-through etc in the BGW210, with many instances of AT&T re-setting the BGW210 to their idea of normal, undoing manual config etc. These discussions are dated 2018, 2019, .... has everyone given up? Or is there another solution?
(I don't understand why wifi APs can't just accept DHCP for their own "WAN" port, then choose a different RFC1918 or whatever subnet for their own DHCP. 10.x, 192.168.111.x, etc, and eliminate a huge class of customer hassle. But that's not pointful here, I'm just whining).