There is a lot of diy spirit in single board computers. The other day I helped a local tv station utilize a raspberry pi 3 as a video stream mirror. The $35 dollar computer can replace a dedicated machine marketed for this purpose costing $900 dollars. It only took about 12 lines of bash to make it work.

Computers today are almost always networked but not many know just how that happens. The equivalent today I'd say is knowing about ethernet, TCP/IP, http, wifi, bluetooth and being able to connect things. IoT will make this feel like dip switches again.

That world doesn't exist anymore. Computers in the 80s was far smaller a field and had less societal impact. Today, pretty much every human in the developed one has access to a computer (a cell phone). The ecosystems are lot more closed today than they used to be.

I like what the other person posted (webpage) but it isn't obscure. I'd say compiling your own Android image and putting it on a phone.

Maybe HardMod or SoftMod of a games console to run homebrew and play pirate games. That's usually a one off process though.

Some of the emulators have some settings that people can noodle around with, and so if you're running it on limited hardware (RPi, RPi Zero) they can be useful to get better performance.

Building a webpage, or programming if any kind.