I've been thinking this a lot lately, searching for things like: a detailed block diagram of the Linux kernel, how page tables work, a comparison of function call ABIs on different platforms, details about low-level network protocols, reserved Linux PID numbers, etc.
Occasionally I would find a Reddit thread with an answer, but it was mixed in with the usual Reddit dross, and I doubt that Reddit is a reliable place to store knowledge. StackOverflow was particularly unhelpful, as the questions are mostly oriented around accomplishing particular tasks, and the answers are necessarily brief.
Nowadays, for general knowledge, I skip Google's enshittified search and go straight to Wikipedia, but Wikipedia has limits on how much detail it will go into about technical topics.
I wonder if there's a need for a comprehensive wiki for all the details of computer guts? There are lots of scattered resources, but having them all compiled in one place would be awesome.