[camtarn]

I suspect that microprocessors might be the sticking point. It's possible to manufacture small integrated circuits in a home lab setting, albeit it's certainly not easy, and you're still reliant on an industrial chemical supply chain for the raw materials. You might even be able to get up to the level of a microcontroller or an older microprocessor. But, as I understand it, modern microprocessors are really difficult to make without very specialised machinery and a lot of proprietary knowledge.

High density data storage would probably also be an issue. And I'm not sure about batteries - I don't know how much proprietary tech is required to make the difference between a basic functional lithium battery versus one that actually stores enough energy to be practical.