Where I live, most restaurants I’d visit have a sign up in the door saying “filming and photography inside this restaurant is prohibited without permission from management.”
If I see someone waving a phone around, I just wave at the nearest waitstaff and point, and they take care of it from there.
It’s tricky though, because a restaurant doesn’t want to get plastered all over YT or IG either. But at least they can point out the fact that it’s clearly posted on the door.