For what it's worth, I figured I'd at least put in an SE support ticket. Filled out all the relevant info for the Connection/Network Issues form.
I'll share any updates I happen to get, although I'm assuming I likely won't get anything too relevant as I'm likely not the only one with a support ticket in for this issue right now.
Definitely frustrating that I renewed my sub only to not be able to play the game. The lack of any form of response after multiple days of an obvious issue is probably the biggest disappointment.
Edit: Received a very boilerplate-y response going through the usual stuff. "Turn off background processes on your computer, this might be caused by Microsoft Edge (lolwut), forward ports on your router, otherwise this is an issue with your ISP so take it up with them" sort of a deal. Replied with some traceroute screenshots showing ping issues at the NTT nodes and emphasized that this issue is not within my control or necessarily fully within AT&T's control. Sooooo we'll see what I get back.