To be clear while the annoying firewall has been a forever thing, and even grandmas know how to use VPNs day-to-day to access Instagram, a full, long-term blackout, has been a relatively new thing, so I don't think there's enough prep for that. Bitchat was certainly something that was spoken about after the January protests and before the war broke out. There was even a thief who cloned and renamed it something Persian without attribution and with shady security and the Bitchat guy got upset about it just a few weeks ago.

There are some government-sanctioned messengers that apparently keep working but some people would not use it as they are completely insecure and watched by big brother, of course. The biggest issue is getting data out of the country not internal comms (e.g. video evidence of massacre, for example, so that some poeple like in this very thread don't get the ammo to whitewash the regime, intentionally or accidentally.)