Is there a serious MOOC that gets into this? I'd like some academic rigour rather than some kid on YouTube. I tried the Unity route and had issues with shaders. Trying to get into GPU programming.
For 3d Objects: 1. Create a mesh. There are a lot of tutorials/free asset store helper classes that can show you how to do this, alternatively just copy the mesh out of an instanced object 2. Assign a pre-made shader to it 3. Render it with OpenGL, e.g. GL.DrawMesh/Instanced
For general starter OpenGL you can just make calls using GL.Begin etc.
The nice thing about doing this is that things like lighting, shaders, OpenGL state switching/machine etc. are already taken care of for you (and those little things can take a long time to figure out if you're new).
If by GPU programming you're thinking more compute focused than graphics, reading Nvidia's CUDA documentation and tutorials could be a good start.
I suspect Vulkan will require the same sort of effort. I bought the Programming Guide in the first preorder campaign, but I think the way I will learn Vulkan is by transplanting my pet ES2 projects into an existing Vulkan skeleton.