The guys are MickeyMentol & LittleCage. One was using wired, didn't notice the other. One Win10, one 7 if it matters. And yeah I'm not crazy about trying that custom firmware even if it's supported, something I have no experience with & can't even say for sure will work.
E.mikaelson suggested using a free vpn -- I tried out tunnelbear just now, it's super easy and it works fine. I was able to play a 3v3 game with no lag for anyone, idk if it'll help their problem but it's worth trying! So if you read this guys go here and download it: https://www.tunnelbear.com/download
Install & run, set up an account, then just pick the nearest location & click the switch to On and see if it works. You only need to use it on one PC and whoever is NOT using tunnelbear will need to host the game. Let us know if it works!
(that's totally the oatmeal bear isn't it...)