Large ISPs (AT&T, Comcast, and others) have intentionally removed or never implemented the ability to configure customer-specified DNS servers via DHCP in their branded gateways. The workarounds are to either configure all your devices with static DNS settings or to install and configure a replacement router.
[DNS] pros and cons of using Comcast's DNS servers Mar 10, 2014 Unusual access | DSLReports, ISP Information Forum discussion: Hey guys, I just had Comcast High Speed Internet installed about a week ago, and so far I'm loving it! I just can't decide which DNS Servers to use though. Back when I had AT&T Free and Public DNS Server List (Valid July 2020) Jul 01, 2020 Talk about the fox guarding the hen house. Comcast to
How to change the DNS address on comcast router – OpenDNS
Comcast fights Google’s encrypted-DNS plan but promises Comcast also said it deletes DNS queries generated by its Internet customers every 24 hours "except in very specific cases where we need to research a security or network performance issue, protect DNSSEC - Comcast
Fixing DNS Woes for Comcast Users and Everyone else | ZDNet
Jun 18, 2020 How to Double Your Internet Speed With One Settings Change Jul 09, 2020 Comcast outage map | Downdetector Comcast offers cable television, internet and home phone service. Services are branded Xfinity in areas where digital triple play services are available. Xfinity TV offers television over the internet (IPTV). Comcast serves homes and businesses in 40 states and the District of Columbia. Comcast is a majority shareholder of NBC Universal.