So, a later update, sorry the wait.
Opening up ports is usually a 'hail mary' type of solution because it means something on the edge is a problem somewhere; no one should be screwing with their ports unless they have a very specific or problematic connection to the internet. But it's easy to do, and a valid step in the troubleshooting process so you can say 'everything on my side is open, so it's not that'.
Funny enough, I go to find out this Spectrum supplied router doesn't even have a web GUI - it has a QR code that wants you to download an app onto a smartphone. Can you believe that?
So to do so I need to bug my roommate to auth me as a user so I can even start this process, because it's not just a user/pass situation to get into this thing, he actually has to manually add me as an authorized user on the account. I don't feel like bugging my new roommate over 'one of my games doesn't play right, please give me all the access' so I put it off for a while.
I eventually get the access, and the the app on my phone. It's awful, it leaves out so many technical details and options from a normal router config. In fact I go to open up the ports and for some reason it doesn't save, probably because I'm not the account owner.
But I try Apex again during this time, and praise be, it just works. So my original suspicion was correct; there was a misconfig or problem somewhere in my ISPs connection to the wider internet, and I just had to wait until the Network Engineer who had that ticket in their queue got to it.
So sorry for this boring post, but I think the lesson is, if a game was working fine and then didn't for no reason, almost certainly the issue is in the wider internet beyond your house and you just have to wait until the level 2 support gets to the ticket that will fix it.
