Real time chat: wild unsecure simplicity proven to run anywhere (IRC), bells & whistles with contemporary security (Matrix), some mesh native that almost no one knows ? What about post-disaster onboarding of actual users ?
Store & forward messaging: SMTP & friends may work nicely, but with actually distributed servers - in each local disaster POP. Also needs timeout and retry parameters to keeping stuff in queues practically forever.
Forums: anything better than ol' NNTP ? Other protocols merely adopted intermittent indirect connectivity - NNTP was born in it !
Is anything more sophisticated or more interactive realistic for actual disaster ?
An onboarding kit with clients for each major OS (à la AOL CDROM !) might be handy too, for snearkernet distribution over USB dongles.