It's 2019, people carry electronics everywhere. Mark is 70, not 270 years old, and surely there are more "up to date" people around him to explain that this battle is long lost. Most people who film are probably not aware of their lights being a problem, and a GENTLE REMINDER works alot better than calling for security or being grumpy and point fingers everywhere. Also from a show perspective, it is just embarrassing if an artist gets pissed off at this kind of behaviour to the point where they're visibly angry while on stage. If the guy is front row, why not approach him, make a funny face in his camera, and whisper "dude that flash makes it hard to focus on playing the songs, please turn it down".
If that doesn't help, sunglasses indoors?
Honestly, if I paid 100 Euros for a show and half of it was spoiled because of interruptions from nonsense like "oh noes, someone filmed on third row", I'd be done seeing that artist live. I pay for the performance, not grumpy noises from center stage, and non-vital security interactions.