Yeah I think so. There are some optimisations that can be done to improve things, but at the end of the day it’s running off a slow USB drive

I’ve just got Arch Linux installed on a USB drive. I set it up so it works with both UEFI and legacy BIOS boot. It works great - I can install whatever tools I need on it, I can even use it as a little portable Linux drive if I need that. I’ve also used it to install Arch on a number of my computers.

The only issue is that the USB drive is pretty slow, so it’s not the best experience using it

I doubt it - the bootloader is very different on iPads and I don’t think it would let you boot a different OS