I had this same daily connection disruption problem with Xfinity on the east coast, on two different lines in the same building.

But, one difference is that the two lines would fail at different times, not at the exact same time (so not the cause guessed by Gemini, in my case).

I always assumed it was Comcast automating downtime to prevent anyone using the lines for business without paying Comcast Business prices.

I had the two locations connected by fiber and used multi WAN for both load balancing and failover, so the combined uptime was basically 100% because each line was down many times per day, but they were always down at different, non-overlapping times.

My guess is that this failure mode is quite common, whether or not it's intentional. I would love to see this be something a lot of us here can coordinate on jointly pushing Comcast to solve!