Used Linux 15+ years professionally. Love NixOS right now, but also Debian

Telegraf is probably a Bad backend for anything. I would seriously reconsider.

While that is true to a degree, it is still worthwhile to have a hierarchy of escalation about on which app or platform it is safe to say which thing and which not.

Not quite sure what kind of privacy you need, but matrix is reasonably easy to self host, and allows you to federate if you want.

Also has plenty of clients.

If you want low tech, hosting IRC is easy too.