PSN mainly

I have a att bgw320-505, and for sometime time all was fine until 2 days ago, my PS5 started acting weird, I ran through everything I could possibly think of and do even up to almost sending my PS5 back but, I found out my son PS5 is doing the same thing, I already talked to Playstation and nothing to could figure out. I call At&t and could see that the house is getting internet but the hardware seemed to have been the issue he said and he could see it failing to a point, so I got a replacement gateway sent out and still doing the same thing, but the trick is everything else works fine except the Playstations and doing research I seen others having the same issues to where the ISP is having issues with certain servers, I've tried port forwarding, speed test, ping test to no fix. I put my Playstation on my phone hot spot and it works flawless except it lags due to it not being what it truly needs to run. I'm in East Tennessee area code 37912.  Anything that requires online gets errors signing and it's not allowing the PSN to sign in fast enough. So through a ridiculous amount of searching I seen it could possibly be a hub issue but how would I inform them of that let alone get someone to understand this when everyone is saying their side is okay.