Other Flex game options: Vikings-Bengals Bears-Browns Steelers-Colts Falcons-Colts
All of these games are labeled as flex games for 12/16 or 12/17. Not sure if there is a Saturday night game on 12/16, but the rest of the options seem like bad options.
The traditionally announce about 12 days ahead of time (so expect Tuesday the 5th).
Last year the flexed Bills vs. Broncos to Saturday night, as that was the option with the best two teams. Given that, it stands to reason it’ll be Lions vs. Broncos on Saturday night.