I have less experience with shows (never had an issue but also don’t go to a lot) but in terms of flights: it is still very worth having a printed ticket. Because maybe one in ten times the scanners will have an issue due to shitty outdated scanners coupled with gunk on phone screens.

But also? Don’t print your plane tickets at home. Just spend 2 minutes with the kiosk while you take off your belt and whatever else you have to do and print out the slip of paper before you go to screening.