Oh man, the classic parental worry! Been on the receiving end of that, for sure. Most parents I knew, and mine too, leaned into the built-in screen time controls on iOS and Android, and sometimes checked Wi-Fi logs.
Honestly, a lot of the hardcore monitoring stuff just made me better at hiding things. What actually made a difference was when my parents had clear rules and we talked about why they were worried, alongside some basic screen time limits.