This question explains in detail why it's basically impossible to boot Linux from a USB stick.
But I am still wondering: is it possible to load and "boot" a stick-bound Linux distro from a USB stick using the Termux terminal app? It can already access files from sticks and run other distros like Arch, so I'd imagine it to be quite possible.
I'm open about the specifics. I'll take whatever distro works.
The idea is to setup a stick-bound persistent Linux instance for specific tasks. I want to run this Linux both on PC and android through the same USB-Stick, although I'd settle for an android-only solution at this point.