I have been using Linux as my daily driver for quite some time (around 5-6 years) and usually manage to get whatever needs to be done. However, I now wish to learn it in a more structured manner, which includes understanding utilities and the workings of Linux. What resources should I look out for?
I disagree. Sometime, a structured approach allows to discover things you don’t even know exist
Structured approach to what? You don’t take a structured approach to a hammer, you use it as a tool to accomplish something.
”The Linux Programming Interface” is an excellent book, if you are interested in interacting with the Linux kernel directly, but somehow I doubt that’s what OP wants to do. I doubt OP knows what he wants to do.
Besides, please note that I did encourage taking a structured approach to stuff discovered on the way. But taking a structured approach to ”Linux” is just a bad idea, it’s far to broad of a topic.
Edit: RedHat has their certification programs. These are certainly structured. You’ll get to know RedHat and the RedHat^{TM} certified way of doing things. That’s probably the closest thing to what OP wants. You even get a paper at the end if you pay up. This is not the most efficient way to get proficient.
Structured approach for hammer would be probably learning when not to use hammer I guess?