The only real long-term survival platform is an isolated farm where you can grow your own food.
Nomadic is fine, but the cannibals they encountered on their trip would have eaten even the homeless guy with the shopping cart.
And nomadic has certain risks -- uncertain access to food or water, crossing paths with other dangerous nomads, crossing into territory held by hostiles, exposure to weather and so on.
It's amusing to think about survivalism but really, things go south without a community structure pretty fast. Even a very isolated bunker has a limited timeline without access to outside resources -- 5 years, 10 at the outside for a large quantity of food stuffs amenable to long term storage? This also assumes you have no energy needs, dependence on anything that might wear out or need repairs unless you have multiple replacements which don't age in storage.
I suppose someone could treat a bunker like a long-haul space ship and provide it with a nuclear power source, a water recycling system, air filtration and the necessary parts and replacement equipment to keep it running but even that becomes a challenge past a certain timeline and requires extensive skills and a large community, and the community itself can become a liability as people aren't totally dependable.