One common concern many independent learners of computer science and tech have is figuring out what they "don't know". More specifically, the concern is that since they've never been formally educated in CS, their knowledge might have "blind spots", which can cripple them when they start working on more complex projects or try and get a job. (For example, somebody who didn't know that data structures and algorithms were a thing will very likely struggle on most standard tech interviews).
I interact with/help self-learners on a fairly regular basis, and am never quite sure what to tell them when this question comes up.
One strategy, of course, is to simply give them a list of things they ought to know -- there are many articles that give a good overview of topics covered by a standard CS degree, for example (example 1, example 2). However, this strategy doesn't generalize well: once you move on to trying to learn about something not on some list, you're back at square one.
The other strategy I try suggesting is to just read random highly-upvoted posts on StackOverflow and news aggregate sites like Hacker News -- I've personally found you tend to pick up a good awareness of different CS and tech topics almost by osmosis if you do this. However, this strategy is also flawed: it's a random and slow process, and isn't guaranteed to be comprehensive. (If a topic isn't trendy, it's likely you'll never stumble across it.)
This brings me to my core question: what are some effective meta-strategies suitable for self-learners that help them identify gaps in their knowledge?
I'm hoping for strategies that are either more generalizable or more systematic then the two I listed up above.