There is/was already a social network for that - Ning. Back when social network platforms became A Thing they adopted OpenSocial - they had a news feed, notifi

There is/was already a social network for that - Ning. Back when social network platforms became A Thing they adopted OpenSocial - they had a news feed, notifications, etc - but each social network was completely isolated. I haven't taken a look at Ning since I worked on social networking apps about 12 years ago, so I have no clue how they've evolved since then.