Other replies already addressed the screen time/hanging out together aspect, so I will comment on being unsupervised. I was a kid on the early-ish internet and I was free to "surf the interwebs" unsupervised. The internet is not the same anymore but I think the general rules still apply. This was a very valuable learning experience for me. Based on my own experience (anecdata, I know) what I found really helped me is…
To expand on this, with the $CURRENT_YEAR generation of kids, it is very likely that the first scam they will encounter will be a Discord or Steam related account stealing or malware scam.
These are the specific examples that everyone using Discord should be aware of - https://i.imgur.com/PPni16I.png