I don't know everywhere in the world, but at least in some of the poorest countries of West Africa, in the low-to-middle class (merchants, a large part of bike/

I don't know everywhere in the world, but at least in some of the poorest countries of West Africa, in the low-to-middle class (merchants, a large part of bike/car taxis, salesmen, teachers, IT...) everyone have a smartphone, using heavily Whatsapp btw. This is the kind of hw that will most likely remain after a collapse. Survival should concentrate on using smartphones for general purposes, while trying to not depend on online services (AppleStore, PlayStore etc). As a side note, survival best practice would be to depend only on what is the most likely to remain. Programmers knowing the mainstream languages are the wide majority, so after losing lots of people, they are the ones most likely to be still around. Better build an OS based on C/C++, Java, JS.