Per the Verge if you have one of the 4K comcast boxes.
"with an X1 box: say “4K” into your Voice Remote, go to Sports, and select NFL on the guide, or go to the X1 Sports app and open the NFL tab"
It's usually on the sports guide
there's a link to the 4k stream.
as it's not a channel but a stream.
thats how I been watching College football in 4k. all season long.
The short answer to how do you access the Packers - Eagles game in 4K on Xfinity:
Without so much as a notice on the TV when you search for it last night, Xfinity at the last minute dropped out of offering the game in 4k. No explaination. This is from "The Verge" (a pretty good tech source) "Comcast pulled the 4K HDR feed from its cable lineup at the last minute for unspecified reasons."
I guess Comcast just decided to take another dump on their customers.
doubt they will do any 4k this season. What a let down! For what they charge their customers, they should be able to deliver since they did for World Cup!
I would recommend contacting FOX.
They are the ones using new equipment for 4K and HDR. Since it is new they may be having problems doing HDR (1080p) or 4K sent IPV.