Warhammer 40K brought a lot of adults into miniature painting during the pandemic; the hobby is bigger than Games Workshop and has always been. This is a working syllabus for the painter who wants to know what else exists: the non-Games Workshop companies making paintable miniatures, the 3D-printing revolution that changed what a miniature costs, the paint systems past Citadel's, the techniques the beginner tutorials skip, and the instructors who taught the current generation of award-winning painters. I have deliberately not included any Etsy resin-recast recommendations; the ethics are complicated, and it deserves a separate conversation.
The rest of the industry, with actual product lines and real design pedigrees. Sculpts you can paint without buying into a wargame system.
Resin printers made every fantasy sculpt in the world available as a file for the price of the resin. Where to start, what to print, whose files are worth the money.
Citadel is fine, expensive, and everywhere. The alternatives are cheaper, better in some technical ways, and give you a wider range if you commit. Do not mix systems until you understand each.
Edge highlighting, glazing, non-metallic metal, source lighting, freehand. What the winning entries at Golden Demon actually did that a base-shade-highlight video did not teach you.
The paid instructors who taught the current generation. All have free content on YouTube as well; the paid classes are what to invest in when you know you want to level up.
Where the scene actually lives, and what to read to understand it beyond the paint-and-brush conversation.