Yes, it is. Most articles there are practically API-agnostic. Just because the code examples happen to be written with OpenGL it doesn't mean it's about OpenGL.
https://learnopengl.com/PBR/Lighting
Even the code snippets start with "#version 330", if you implement these in another tech stack (say vulkan+slang) the relevant shader code would look very similar. It's quite strange to me that you think just because of "#version 330" it's not about fundamentals, tbh.