My hottest “I have no data to back this up” take is that phones aren’t making young people less happy. What’s making them less happy is living in a world where everyone is having their reality defined by recommendation algorithms that can only care about whether something keeps you watching.
Or living in a world where generations are worse off than our parents.

Or living in a world where wealth had been hoarded to literal comic-book villain levels.

Or a world with the creeping ascent of rightwing authoritarianism.

… Or living in a world where it’s harder to live in blissful ignorance of all that and everything else that’s going on.