Gigabit Plan - very slow upstream (speedtests often less than 1Mbps) - Arris SB8200

For the last 6 months I have been having problems with Comcast and my speeds, but problems have been happening for a couple of years on and off.
I will usually notice that in a Discord chat my friends say that my voice is sounding robotic, and when I run a speedtest it's always the upstream that's problematic.
This almost always happens around 4-9pm.
I am in a single family home, not an apartment or condo complex.
My PC has a direct Cat6 connection - no Wifi use.

I have gone through all the troubleshooting steps with their phone support, many times they say they can't 'see' my modem.

I hade one tech who came to the house in 2019 who said that he suspected old/failing cabling under the ground at the back of our house that likely needed replacement, and he would call in a 'work order' to have this done. It never happened, and after 6 months Comcast denied ever getting a 'work order' or that any tech had said that.
I did have this tech's cell number (really nice guy) but that has since been cut off.

This happened yesterday, and I have a tech coming to the house today in about 4 hours, but got an automated message from Comcast saying I might want to consider cancelling that service call as they 'identified issues in my neighborhood that have been resolve' - their site reports no outages in my area yesterday.

A call directly with Arris tech support have assured me that the upstream levels are the problem, they are below their 45dB MINIMUM (range is 45-61dB), but I have had Comcast basically say Arris don't know what they are talking about in the the past.

I don't expect much to be improved, but at the same point I don't expect the tech to do anything either, other than stomp around for a bit and then say nothing is wrong (again).
I'm at a loss as to what to do?

Here's some logs from the Arris Sb8200: