I suggest Anton's OpenGL 4[0] as a starter guide for modern GPU pipelines.
For a general graphics introduction I would recommend software renderer tutorials such as this JS one[1]. The problem that has made people split on whether to directly study modern OpenGL is that 1.x is much easier to configure because more parts of its pipeline are fixed-function. There are fewer lines of code involved and you have fewer episodes of "why doesn't it draw anything". Software rendering lets you get around that because you configure only exactly as much as you have built, and because you built it you understand it(to some depth). When you go to any current GPU API you have to grasp both what the hardware desires and the concepts you're looking for, and in practice the safest way to proceed is to very gradually build up and extend an example codebase so that you have a testing sandbox with easy to toggle modes for debugging, and then adapt that into the application.
I would not bother learning anything before OpenGL 3. The core stuff from 3 onwards is still reasonable for use today, and most changes build upon it rather than fundamentally changing the model, but the older stuff is quite different.
