It’s veering quite a bit into the offtopic territory… On the other hand though, the topic of discussion is related, since it’s about knowledge of using the engine.
I do understand where people are coming from, I wasn’t very experienced when I first started playing around with the engine. And there’s still a lot I don’t know. I had to scratch my head and grind a lot to get stuff done, and a lot of it was done - badly. But it all helped. I finally then went on and got into the introductory C++ course for Unreal that ran 200+ hours on video material alone. It helped a lot, but that’s also a lot of stuff, not all related to Unreal, and I had to do my own testing to really understand the concepts, so I don’t even know how to begin to extrapolate the video hours into hours spent studying.
And, though I did not go through the last project in that course, I’m fairly confident it did not go into using modules. It was rather heavy on stuff but IIRC it also did not cover how UPROPERTY() adds a variable into memory management, for example. And I’d disagree with a lot of the stuff done in that course with my current level of knowledge, but I also appreciate how much further I got after doing it.
I think it would be rather helpful to go through different levels of “mastery” to what there is to Unreal, figure out which topics each level of mastery needs to cover, categorize them between a type (generic programming knowledge, math, and the engine systems themselves) and then try to cover them through the best you can via the training materials. That way topics could also be labeled and people could either go through a related exercise to test their knowledge or go through the material to fill in the necessary gaps or whatever they’re interested in right now.
But there is also the trap where people end up only doing tutorials and nothing on their own, when a lot of time should be invested into doing things on your own, as that’s what the aim is to eventually do.
Epic does have more material on modules, which goes to show how scattered the information is. The documentation on modules in “gameplay modules” documentation section is better than the similar UBT one, though as learning material it’s inferior to the third-party wiki-style one. Unreal Academy also has a course on plugins, which are modules with few extra steps, and you could probably understand how to build a module (and a plugin) through that.
I taught myself modules with the Unreal Fest video on how they made a loading screen in the ARPG example project; that’s on youtube, and the project is freely available on the Epic marketplace. I learned soft references the best from another video from the same guy from Housemarque who made the previously-linked module video on Youtube. Yet I still haven’t used soft references, because I haven’t had the need for them.
Right now with just the official sources of information, we have the forums, the answerhub, youtube/twitch, the unreal academy, the documentation, and the example projects. While it is convoluted to check that many places - though if you use search engines that’s somewhat remedied - it’s also very understandable why that is.
The Youtube material often covers stuff like new tools which are still very much subject to change, like the procedural animations editor or well, what Niagara was. Unreal academy has more structured courses. Documentation is the official reference. Example projects show practical applications. Forums have discussions. Answerhub works as an answer repository for questions, though even most helpful topics are years old by this point.
But even with the best efforts made, you will still end up at a point where you are better off doing your own tests and reading the source code. That point should be further in into using the engine, yes, but I think it can never really be completely eliminated.
no. Discourse is trash, has been trash, and we ALL (check feedback forum thread to cringe some) told you not to implement it before whoever decided to do whatever the 
like ten years ago).