@andycarolan
Yeah, I'm doing something similar, but with a computer. We're leveraging a supervised YouTube account (more or less the last Google service standing since Small Owlbear made the shift to Firefox) and I'm manually restricted some games from the family Steam library.
But most of my approach is being available to talk about stuff, making computer use a shared family experience (which my mum did for me when I was growing up), and explaining what the blocks are for.
I've shown them how to use private browsing to circumvent the adult content restrictions I put in place, but that's also something they come to me to discuss, and we've talked about what kinds of adult content they'd rather not see (the boring, the horny and the too-scary) and the kind of content I'd rather they didn't see (bigotry, extreme violence, animal cruelty, exploitation).
Some stuff, we had to talk through with extensive explanations (why I'm not comfortable with a lot of military content, for instance) and reach a compromise (obvious pretend play only and some explainers about how military propaganda works and why it's bad).
It's definitely a labour (and to some extent expertise) intensive approach, but given that I don't want to still be managing a content filtering system when they're 13, talking stuff through is the only sensible option I can think of.
A combination of adblockers, strong network security and a relatively untargeted OS choice (Pop!_OS Linux in this case) take care of the malware threat side of things.
But none of this scales evenly. I have the privilege of time and expertise, but as with so much of online life, a lot of people have just been chucked in at the deep end and told to start swimming, with it pitched as somehow being their own fault if they drown.
@neil