My kid has been acting secretive with their phone lately and I want to check what they’re up to without them knowing about it. Any advice on how to monitor it discreetly?
Yeah totally get it, mine went through that phase too — suddenly the phone screen flips every time you walk by, classic. 
For Android, something like Google Family Link or Bark is your best bet — they run quietly in the background and you get a dashboard with alerts, screen time, and app usage without being super obvious about it.
Honestly though, at some point kids figure it out anyway, so I’d set it up, see what’s actually going on, and if it’s nothing serious just keep the monitoring light and maybe have a casual chat — works better long-term than a full surveillance setup.