I have XFinity service and use a Netgear Orbi router. The DNS option has a selection for - Obtain DNS settings from ISP or - Use these DNS servers. When I select the second option the boxes for setting the DNS server addresses are enabled. I use:
1.1.1.1
1.0.0.1
These are the Cloudflare DNS servers. That coupled with a VPN and Xfinity can't see what I'm doing.