I've been toying with porting a tiny subset of Unix to the Raspberry Pico ever since I bought a pair of these cute little buggers. But memory at 264KB remains an issue. How easy is it to wire up SPI to some external RAM chips maybe on a breadboard?
Yeah you won't even be able to decompress the kernel, you'll need at least a few MB of RAM (and even that would be heroic). Google SPI SRAM, pretty easy to use.
I think it's totally possible if it's all run from the flash and only used the SRAM for housekeeping. Should be fun !