I needed this a few years ago when trying to keep my kids from playing games (subway surfer in particular:))..now they are in college and pretty much outside the scope of this. Really cool app.

I was setting up first smartphone for my kid (6th grade, they were using dumb phone, didn't really beg for smartphone, but don't want them to be social outcasts, so they need Whatsapp and also the new class teacher seems to be pushing official school app for home works and grades a lot, because apparently telling kids what's their home work in school is too much to ask nowadays) - phone is degoogled Lineage without Google Play Services, so no Family Link and I didn't like the idea of Google (account) being involved in setting time limits for my kid.

First choice I tried was Open Timelimit, but failed since it didn't work as Device Admin, I wanted originally keep parent profile (admin user) in the phone and create new restricted child profile (other user), but with Open TimeLimit child could still easily disable admin app or accessibility permission making OTL unusable (it can warn user it was tampered with permissions, but can't do anything about it to avoid it).

Now full TimeLimit in local mode works as expected, though only with one shared profile (everything under one Android user) - you have one Android user in the phone, you install the app, it will act as Device Admin, so deactivating admin app is impossible and disabling accessibility or overlay will lock the phone completely, so child should be unable to avoid restrictions. There is no easy way to completely block the apps, though you can set them for 0 hours 0 minutes, so they will immediately close upon launching. Other than that you can set whatever app categories you want for unrestricted apps or partially restricted apps where you can set different time limits per workday and per weekend, you can also restrict Package installer, so kid can't install downloaded APK from whatever source and also can't uninstall any apps.

Another problem was creating parent managed Whatsapp account, official Play Store version didn't provide this feature in my region (Czechia), so I had to download latest beta version from APK Mirror where this option is present, on screen for entering phone number you have to tap top right corner three dots and tap on parent managed account and then the process is pretty straightforward, you have to verify you are adult on your adult (parent) phone with selfie. Just so you know parent managed whatsapp has nice clean layout with no AI, no status and other crap, I wish they would offer this for adults, only major con is no dark mode possible to set in the app.

Nobody really use e-mail among kids, but wanted kid to have one just in case, already even created Proton mail account on desktop, but was surprised they don't support 3rd party apps on Android and even more surprised they require Android 10 to install latest version (the old phone I gave to kid is A8.1, Lineage 15 and please enlighten me how unsafe it is if kid can't open even browser or system webview), so F that, good luck attracting new users with this approach (similar to grapheneos paranoids) and went for outlook.com account (Nine Mail app) which can at least sync also calendar/contacts.

Fun apps (30mins total daily limit) I installed there - 2048, Braincup, Duolingo, Open Sudoku, Temple Run, Wikipedia - told kid if they wanna play games they have PS3 or videogame, if they wanna browse they have laptop available, they don't need access to these all the time in pocket.