There are also several good museums dedicated to the subject. I used to work for the national museum of computing at bletchley park in the UK, and there they have a lot of good exhibits that teach basics of how computers and networking works and has evolved over the years.
Another good approach one can take to learn is starting with a simple system with well-defined rules, and making a simple computer out of it. Many people do this in minecraft, for myself it was boolean functions in excel. You can and should look many things up during this process, fail and rework designs several times etc. Learning how logic gates work, then scaling the knowledge up to bit adders, registers, ALU, making a cpu instruction set and starting on basic turing machine architecture is a very rewarding hobby and is definately the best way to get low-level knowledge
Note that there are two museums on the site of Bletchley Park, with different opening hours -- the historic site, including the main house and the huts, and the separate National Museum of Computing, which has the Colossus replica, the WITCH, and a large collection of other British computing machinery and memorabilia. If your interest is in computing history, you'll probably want to see both -- which means timing your visit when they're both open, so be sure to check.
if you do go, my favorite exhibit at Bletchley is the Harwell Dekatron a.k.a WITCH. It's a really good machine for learning how computers work, both because its so early meaning it has simple architecture, but also for other reasons:
It uses base 10 instead of base 2 to store values in its memory, so doing the calculations in your head is a lot easier
It's memory is made from special tubes that have a orange glow at one of 10 positions, meaning you can see the contents of the computer's memory in its entirety just by looking at the machine.
Building off the previous point, you can see the cpu register, which is a single small piece of memory that stores the current data to be modified, which again with the lit-up memory means you can see what the computer is doing at any givenm time.
Finally, the computer has a debugging switch which can pause and step forwards through each instruction the computer is performing, as well as a more granular mode that lets you step through individual parts of an operation (for example each digit being added in a adding operation separately)
It's not always running but if you go I hope you get to see it :)
EDIT: oh and I suppose I should mention there is more than one museum at bletchley, there is the big one that focuses on ww2, but the museum of computing is tucked away to the side a bit.
Another good approach one can take to learn is starting with a simple system with well-defined rules, and making a simple computer out of it. Many people do this in minecraft, for myself it was boolean functions in excel. You can and should look many things up during this process, fail and rework designs several times etc. Learning how logic gates work, then scaling the knowledge up to bit adders, registers, ALU, making a cpu instruction set and starting on basic turing machine architecture is a very rewarding hobby and is definately the best way to get low-level knowledge