Hoping this helps those who have this issue:
I had to set a reserved IP in Xfinity modem settings and then manually configure my network adapter for that same IP, subnet, gateway, and DNS servers for my ISP.
I did this for IPV4 and for IPV6 I just set the DNS servers in the network adapter.
Then, on my computer I searched regedit for all instances of "utopia" and cleared the value data.
Restart computer and if all settings are configured correctly, you should have full IPV4 connectivity.
You can get internet by just setting the IPV6 DNS entries on your network adapter and disabling IPV4 if you cant get to the router config page. But you wont be able to use some services, such as Steam, if you are on IPV6 exclusively.
FYI, the issue appears even after a clean windows install and after a factory reset of the router. Connect fresh install to the factory reset Xfinity modem for the first time and it pulls the "utopia.net" dns suffix immediately. Search registry and those three "utopia.net" entries are there.
Good luck out there.
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