There are many tutorials.
If you check the Tutorials section of this forum, there are a lot of textual tutorials. Agreed, the manual is brilliant, but it's out-of-date and I think I need to personally ask on the lmms discord for permission to edit it. I don't have nor can I get a discord account.
I never really "learnt LMMS" through the manual as such, rather finding my own way around and figuring out how things worked. I got an EQ VST, which was the first third-party sample/module I'd ever used, and now find LMMS-graphic EQ far superior to it. Later started with soundfonts and the like. Initially learnt the song editor and piano roll, then B/B editor. Controller rack and mixer came last.
Would I have a better grasp if I started from ground up, following the manual or anyone's tutes? Probably. But my style of learning involves my specific requirements and quick fixes for small things I want fixed, rather than following a long-term plan someone else makes. I find it near-impossible to stick to someone else's course, and dislike the idea.
That being said, I personally guarantee that LMMS is one of the most intuitive DAWs I've encountered. It's also the most painless when it comes to absurd limits, primarily because there aren't many.
The point is that I never went through anything remotely like your learning curve, and therefore don't have many resources or suggestions at hand.
If you want video tutes, you can check:
musikbear's youtube channel
here, where musikbear uploads all sorts of tutorials, they're slightly slow-paced if you like that sort of stuff and otherwise good.
Cubician (Ian Sannar)'s youtube channel
here where he teaches you specific techniques and how LMMS and parts of LMMS work, he tends to deviate a bit but it's still good quality.
Otherwise, looking up "How to use/do [whatever you're looking for] in LMMS" on youtube should get you anything you like.
