Well that was a giant waste of time. After everyone went to bed I tried to swap to the new modem Comcast sent vee.
The pathway that claims to not require a smartphone app suddenly halts half way through activation and tells you to download the app with no way to continue. The app is 300mb of react shite I had to choke down over my 1 bar connection from the living room because, you know, my net was down.
The app crashes on launch. Available support flatly declares "We cannot support activation issues until you get far enough to pair the modem with your account, use the app"
I am incensed.