And that's hardly something there's an easy how-to answer to.

A primitive tribe or band tends have each member strongly connected each other member since with few resources, the people are the resources. Modern people don't have to care in the slightest about their neighbors and this is weakness in an emergency situation.

Moreover, a "collapse" situation, in many instances, would imply a general social failure even more complete than recent problems we've seen (consider "I'd rather X many people die than the economy suffer [from Covid or limiting carbon pollution or etc"] a statement about non-community). I don't know how mainstream society would even come back from that. Perhaps the Amish would do well.