Agree with your points on having a pocked PC to hack with, the issue here is then with mobile and their OS makers which mindbogglingly have omitted to design a working and hardly hackable “children account mode”, since what is damaging here is not what they can fiddle within their devices, nor certainly what they can read from wikipedia, but rather the unfiltered and unaccountable exposure to a profiling oriented social media storm which even adults fatigue to cope with.
I’m sure it isn’t unheard of OSes having a hardware locked managed kiosk mode, because that is what smartphones basically need.
Gleam?
https://gleam.run/