Limited time and very limited access to content, only content that is age appropriate.

Use the device’s parental controls to limit apps, downloading, purchases, sites, hours available and total time allowed. Doesn’t matter if it’s a phone, tablet, or PC. LAN parental controls if available as a secondary layer of site blocking and overall internet blocking at internet curfew time.

Been doing this for years. It’s a must. Parents are responsible for limits on mobile devices and content. Having the software do the limits is far, far easier than physically demanding the phone from the kid, shutting it off, or looking over their shoulder to see what they’re using it for.