I think the answer is personal newsletters. Email is (sufficiently) distributed, and (about) everybody uses it.

I've replaced most of my social email with a monthly update. On the first day of every month, I publish a post on my website titled “What I’m up to this month.” In it, I have three simple sections:

- Highlights from last month

- Things to share

- What I’m up to this month

It sends to my mailing list. I find it works great - I can stay in touch with people, and people bring it up in conversations. It lacks the dopamine hits of "likes", but I think that it's ok to have a calmer, stupider system for staying in touch.