Connection speed is 2% of expected

I reported issues with connection speed earlier this week, and the customer service solution was to send me a new modem and change my plan. I installed the brand new Xfinity Gateway and replaced all of the cables, but the connection speed has not improved. The Xfinity app tells me I'm getting around 20Mbps out of my expected 1000Mbps which is absurdly low. I have tried all of the recommended troubleshooting steps and nothing changes. However connection between devices in my home remains strong.

There is clearly something wrong upstream in the signal, but every service agent I talk to just keeps trying to change my plan or devices again, or tries to schedule 'installation' for a device that is already installed. I do not need a band aid, I need a real solution.