This is unfortunately why I moved the kids devices to iPhone/iPad.
I was not able to find any native methods of locking things down without involving third parties collecting a ton of data.
In iOS I can set their account as a child account, which then lets me
- limit what applications they can launch
- what websites they can visit
- how much screen time they spend in an app or category of apps
- disable in app purchases
- disable pop up advertisements in app
- require approval from parent account for any app download (including free)
- remove ability to delete apps or change specific settings
all with the native iOS settings