Even if you're not much of a tinkerer, Ben Eater's videos are massively helpful if you want to truly understand how computers work. As long as you come in knowing the rudiments of digital electronics, just watching his stuff is a whole education in 8-bit computer design. You won't quite learn how modern computers work with their fancy caches and pipelines and such, but it's a really strong foundation to build on.

I've built stuff with microcontrollers (partially aided by techniques learned here), but that was very purpose-driven and I'm not super interested in just messing around for fun.