I don't see that applying to everyone. Yes that may end up as reality in parts of the world. But there is simply too much wealth in the world to not be possible to create isolated and self contained facilities which still use modern technology.

And we can prepare for such events by deliberately creating simpler technologies which require less complex supply chains. E.g. a modern tractor today requires a vast amount of different parts, such a micro-chips. But it would be perfectly possible for an engineer to design a more old fashion tractor e.g. using a steam engine which could be powered by biomass and don't need micro-chips e.g.

Likewise one can imagine construction of wind turbines and solar power plants using simple technology. After all we got wind mills from the 1600s still around. With modern knowledge it should be possible to make more durable wind turbines if not equally efficient ones.

Likewise you can build concentrated solar power solutions with relatively simple technology. It doesn't require sophisticated silicon manufacture, just mirrors, which is a pretty old technology.