There are no mentally healthy apps to have. You also have to enforce any rules you make and are always already in a fight that you cannot loose. The smartphone is net negative on mental health. I would only make arguments that you can get distracted really easily if you are too focused on something bad. Like today if you become a stalker you really need to be ill because there is so much distraction with the phone that it's hard to see someone healthy become a stalker.

My solution is to do activities where you don't have your smartphone. Something like swimming or riding your bike is great.