What is a good kit to learn about retro-computing?

I know this isn't an Arduino question really, but I can't find a good place to ask it.
I'm interested in learning how computers work, on a really low level. I got a raspberry pi but a while back, but want to know more about the hardware side of things - even diving into how a CPU works inside. I heard about people making their own 8 bit computers in the 80s (I was born in the mid 90s) and am intrigued by this. It seems to be a way to really learn how a computer works in its entirety.
I'm a freshmen CE student, so I understand a good amount of digital logic and such, but want to learn about this on my own as the classes that cover it I won't take for at least a year, and use FPGAs to implement many designs.
Unfortunately I don't have time to design and route a PCB, so I was wondering if there is a good kit out there? I found something like this:

Hello tinkerkid,

I have made a quick search online, and it looks like there are not so many alternatives out there.

What I have found (based on Arduino hardware):

Otherwise, you should try with those 2 alternatives (I am not sure they are still commercially available):

I hope this helps.