IMO the technical part of this is easier than the social part. I've been hosting a Matrix server for years, and use it to talk to my wife and one friend.
One relative tried it but would ignore messages (iOS notification system design is bad, but their home screen is disorganized too), and would constantly revert to iMessage/SMS/MMS.
Two other relatives who are in a WhatsApp group with me pretty much refused with "But I can talk to you on WhatsApp just fine?", or "Who am I going to talk to on there?". Ironically does not stop them from downloading Viber, Instagram etc. Thankfully, the WhatsApp bridge + Matrix client works for 95% of the use cases.
Thus, I am happy that the author's efforts found good use and were appreciated.
A personal social network. No influencers. No ads.
It rides on existing messaging rails (email, SMS, IM…) for distribution.
You just post stuff to your feed, and your contacts get a notification when appropriate.