I've never understood the need honestly. Why use software to control your kids actions? If i had a kid i wouldn't give them a typical smartphone and would give them a stripped down degoogled android phone that has basic functions like organic maps, phone, text, etc. If they want another app I'd tell them to figure out how to install f droid and aurora store and install them on their own. Until they can do that they don't get other apps. Once they've learned enough to do that they can download what they want. Same with a computer. Give them a linux laptop with a web browser, libre office suite, and other basic things and let them figure out how to do stuff like play games, and install other software on their own. Just set it up to do backups to your home network regularly so if they break their OS you can roll it back.
I think this would result in a kid that is much more technologically literate, and much more aware of the dangers of the internet. It's better to let them download a virus and do something dumb now to learn their lesson then to have them make that same mistake once they have their own checking account that can be drained.
You could even do little tests like let them know, "Hey at 5pm Wednesday I'm gonna block your mac address on the wifi. Do some research now, and figure out how to spoof it to get back on the wifi when I do." or buy them a 2nd RAM stick for the laptop and let them figure out how to install it on their own.
Also just have talks with them about like responsible social media use, and how companies collect their data and what they do with it.