Perhaps this gent needs to buy a Rasperry Pi or an Arduino starter kit and project book. That pretty much checks all his boxes for an inexpensive, technically documented, understandable, hardware-exposed, text-mode, resource-limited, off-line capable computer.
It has all the fun hackable qualities of the Apple //e of my youth, except you can buy one for less than $50 instead of the month an a half worth of salary that Dad paid for the //e. $2000 at the time, close to $6000 today, but a worthy investment!
It has all the fun hackable qualities of the Apple //e of my youth, except you can buy one for less than $50 instead of the month an a half worth of salary that Dad paid for the //e. $2000 at the time, close to $6000 today, but a worthy investment!