Frequent service interruptions with no outages reported

I have been in my current home about a year and we’ve had Xfinity since we moved in.  Over the last 3-4 month I have experienced frequent outages - usually lasting only a minute but sometimes 5-10 minutes and on occasion even longer.  If I do a hard reset of the router, it usually resolves the problem, but not always.  In the most extreme instance we were without service for several hours.

I know it’s not an issue with our Wi-Fi extenders because it impacts devices that are using the primary network not the extended network, and it affects Xfinity television service that is also using the Xfinity network.  Often I cannot reset the router using the app on my phone, hence the hard reset I mentioned above.

What is the most effective way to diagnose if this is an issue with my router, or the connection to the house, or the connection from the street?  I had hoped recent Xfinity work in the area might resolve this issue but the outages are still frequent and the service isn’t worth what I’m paying.  Thanks.