The problem is that even if you have a perfectly preserved box of modern cell phones, they're
intentionally not really hacker friendly.
Half the time, you have a locked bootloader, and even if you don't, you probably need a bigger machine to stage and load new software. Even when you're done, you're stuck with a form-factor that's of limited alternate utility. Phones make a decent media player or ereader, but they're not really useful for many use cases. I'd expect, once you've got a few devices up and capable of preserving, say, human knowledge as defined by Wikipedia, you start looking for devices that are more GPIOs and less screen-and-storage. Access to something Arduino-esque could be a big force multiplier, because it allows process automation with relatively low manufacturing skill. Even something like an old mechanical clothes washer timer-- open and close a few relays over time, maybe respond to a few sense switches for emergency stop if the tub leaks-- requires a fairly high degree of mechanical tolerances to get right, or you could implement the same functionality in a few dozen lines of code for an Arduino-esque device, as long as you have the GPIOs. Phones are hardly amenable to that-- you try soldering a big relay to a tiny BGA processor pin.
Some of the documentation seems also focused around the idea of salvage at the component level. This may be a more feasible option too-- when you start to look beyond "computer/phone devices", there are a lot of embedded Z80s and EEPROMs that you could desolder and press into service, and they represent a lot more of a consistent baseline than 400 chips that are all theoretically ARM family, but have wildly different memory maps, peripherals, and varying instruction sets.