lol that’s just not true these days that it’s rude to be on your phone in a restaurant. I’ve seen entire families on ‘em in relatively swank joints, and ain’t no one saying a damn thing.
It’s up to you to use your best judgement. There are many places where it definitely wouldn’t fly (a wedding for example), and it’s up you to read the room.
That said, most casual places usually don’t mind, and when with friends you probably shouldn’t, unless they’re chill. Common sense prevails above all else.
I don't give a shit if you use your phone. But if you take a call and put it on loudspeaker you're the worst kind of person.