I as well seem to be having issues resolving DNS on comcast. 

On Mon, Jul 6, 2020 at 8:57 AM Dave Dechellis <dechellis@gmail.com> wrote:
Hello,

Last night we made some changes to our DNS-SEC environment at Tufts
University and all changes seem to have propagated - but we're having
issues resolving against Comcast's DNS servers.

All DNS-SEC checking seems to be looking good post changes and other
ISPs are resolving fine.

Is there anyone from Comcast who might be able to validate behavior?
I'm assuming it might take up to 1 day for TTL propagation.

Thanks
Dave
David.DeChellis@tufts.edu