Just adding a single data point. My print at home BP was rejected at DEN this morning by TSA but UA were fine with it. TSA person confirmed that TSA no longer accept print at home BPs but want ones on a phone or printed from the airport check-in machines. The fact that UA still allowed me to print a BP at home yesterday when I checked in, with no warning TSA wouldn't accept it, would have been annoying if I hadn't seen this thread.