Shader Courses and Tutorials

Hello, I've been a 3D modeller/texturer/animator for a long time, but I've never properly gotten to grips with shader programming. This is something I want to improve on as I continue to move in a technical art direction, so that I can have a better level of control over content I make, and eventually so that I can experiment with exciting things like SDF and fractals. This is part of a general move I'm trying to make towards a more holistic and experimental approach to 3D graphics.

Put simply, I'm looking for good courses of tutorials that will take me from basic shader fundamentals to advanced techniques.

However, it seems like Unity has a bunch of different paths for creating shaders at the moment and I've heard that certain things don't work with other things.

What would be the best place to get started, and does anyone have general advice regarding URP vs HDRP, Shader Graph vs writing directly in HLSL/CG, forward vs deferred rendering, etc?