I'm only 20, but I'm very attracted to the idea of a computer that a single person could reasonably understand, or at least understand far better than the bloated nightmare of Windows and MacOS. Even Linux is very big and complicated. I'm also looking for simplicity at the hardware level. A Raspberry Pi is cheap, but I would hardly call modern ARMv7 Cortex chips simple.
Are there any computers on the market that try to replicate the simplicity of earlier home computers? Perhaps there's an SBC that would meet my hardware requirements, and there's a separate, simple OS I could flash?
Neither of the 8080 and Z80 chips were considered as 'simple' for that era. And they were so horribly expensive (say about $800 bucks in today's money) that we were paranoid about zapping them with static electricity.
There were several projects using only standard TTL chips and making a usable computer, but they quickly were displaced by the 'CPU on a chip' when the 8080, Z80, 6800, 6502, 2650 and a bunch of other chips all came out. Eventually the wide selection was whittled down to pretty much just the 6502 (Apple) and the Z80 (The main bunch).
http://www.ljw.me.uk/educ8/
I suppose a good question is: What do you want to do with it?
Do you want to learn programming principles?
Do you want to learn programming a particular CPU?
Do you want to learn programming in machine language (assembly language) or a higher-level language (C, Java, Rust, Python)?
Do you have an embedded computer/hardware combo in mind?
And many other questions like those.
And of course, most of those 40-year-old CPUs are still available to play with, anyway. :)
https://www.youtube.com/watch?v=3KAjZbjPqnA&feature=youtu.be