Is it possible to log into someone else's Gmail account for monitoring?

My teenager has been acting extremely secretive lately and spends hours glued to their phone, so I am getting increasingly worried about what kind of stuff they are getting into. I know they use their email a lot to sign up for various apps and chatting platforms, but I have read that just guessing their password and signing in from my laptop will instantly trigger an unverified login alert on their end. Have any other parents figured out a safe workaround to check their inbox without alerting them, or is there a completely different approach I should be taking to monitor their online activity?

Logging into their Gmail without them knowing is tricky and can backfire. I use a parental control app that tracks app usage and alerts me, no password guessing needed—sets up in 5 mins, no hassle. Way easier and respects boundaries more.