[wrycoder]

You can make something as complicated as a 6502 processor with just electricity for furnaces, motors, and pumps, without using any electronics.

You’d have to go back to hand-cut Rubylith for the mask sets.

Hand made transistors are no problem, just more expensive.

[mywittyname]

People still do this stuff for fun too. So it's not some lost knowledge.

I wouldn't be surprised if some colleges taught this as part of a history of computers course.