In short I treat over-use of devices as a symptom and not a cause of social problems ... and they have their share of social problems but they're managing.
Their mom is more strict with phone time on them but they watch unlimited TV. I limit TV and let them have unlimited phone time. At this point their idea of social networking is trolling people in Among Us.
Their mom, my partner and I have helped them build a healthy skepticism for social networks. They basically think they're "stupid" so even though their friends have instagram, and I have instagram, they still think they're dumb and they don't mind that they aren't allowed a social network like that. We're lucky there.
The three of us (especially their mom I feel) have done a thorough job explaining the dangers of connecting with strangers on social networks and they just don't as far as I know. It doesn't hurt that they're fairly anti-social to begin with.
They are paranoid about passwords, the family has our own bitwarden server, and they understand why. Beyond that though they have no concept of internet privacy and don't care what data is being hoovered up by alphabet, apple, etc. I want to try to link privacy and security more closely together but so far I'm not doing great. They spend a lot of time with youtube recommendations and also a lot of time ironically listening to pop music? I don't get it but they love to blast the worst pop they can find and then make gagging noises. I have no idea what the algos are making of that.
They keep secrets from me on their phones. That worries me but my feeling is that if I respect their privacy and focus on building their self-respect then if they have a problem they'll come to me. They spill those secrets to me and my partner occasionally to get revenge on each other and the secrets are harmless. My oldest daughter screen-shotted her sister's browser tabs and made it her background. My kind of petty and I'm proud.
So thanks for this question, I've wanted to get this down in writing to see if it makes sense for ages. Still not sure it does but so far the kids are alright.