I share this interest!

I feel like a lot of ham radio networking is still "offline" from an internet perspective; you may have a LAN or even a WAN but no connection to root DNS or certificate servers or whatever. This tickles my fancy: https://blog.thelifeofkenneth.com/2018/01/off-grid-raspbian-...

I feel like /r/darknetplan is tangentially related, but not quite what I'm looking for.

I've been playing with Internet-in-a-box, which is precisely wrong about its name; it's an offline repository of content that was developed on the internet.

Someday I'd like to marry that with my Othernet receiver, which is a similar offline-hotspot-of-content but keeps that content updated by receiving a satellite data stream. (One-way only.)

Piratebox seems to be a dead project by that name, but I like the idea. A local file repo and possibly bulletin-board for use by folks within range of the box.

Yes, yes, yes, where do we go to chat?

I'm in! I run a small Discord server for 3D printer enthusiasts (I'm building a a closed-loop monitoring system for 3D printers). A section for offline systems in general would be easy for me to add. Invite link: https://discord.gg/sf23bk2hPr

I'm open to wherever people naturally gather though. IRC, maybe?

Another community you might like: https://www.tinyml.org/

I've joined the discord server advertised by grepLeigh in another comment.