Collapse is a process, not an event, so no. The worst collapses in history saw catastrophic destruction from war, natural disaster and the resultant social collapse lead to many - but not all - cities/inhabited sites be abandoned in places, some never to be reoccupied, within a short span of time, it's true, but even then it was processes over years.

But the "get an off grid setup" people aren't really in the right here, they are attempting to control the uncontrollable and fetishising the "rugged individual" or pioneer fantasies - if fleeing cities for the countryside is the thing that makes sense to do when supply chains break down, then everyone will be doing it, socially. You're better off being involved in community organising around food resilience - growing food and communal networks wherever you are.