I'm working as a programmer for about 20 years and invested a lot of time into understanding programming and computers before earning money with it.
I've learned to program Java, use Windows, then Python, Linux. Now I'm a Devops learning Docker and Keycloak ... what I mean to say is: I've picked up a pretty pile of tech but TeX, well ... this always remained a love-hate relationship.
I've made a couple attempts at differents flavours of TeX in the past and was never really happy with the whole thing. In the last month I was using Pandoc over a Docker container, which generates PDF from a Markdown document. I generate the Markdown file from my own Python program. This is fine. I just needed to nudge the default theme and I almost got everything that I wanted.
My problem is: I know I don't master the TeX behind it. How do I learn TeX (or LuaTeX or whatever) so I really am in control?
I want to know about what the nitty-gritty details are. I want to know what consequences are of choosing this flavour of TeX and choosing that package etc.
How do I learn this? What is the starting point to get on that path?
Update: I've read (or at least skimmed over) many tutorials. Some of my recurring problem about those:
Many tutorials aim to teach you how to write a scientific paper in the end (which I'm not really interested in).
Many times the tutorials are old and I'm uncertain if the information is still relevant (just as an example), let's say if I already know I'll be using LuaTeX/LuaLaTeX.
My goal is: I want to know about the today relevant foundations of TeX. About the architecture of it. What the limits of which parts are. I want to be able to make an informed decision about which part of TeX is going to be good about tackling what kind of problem.