The latest edition (7th ed, 2015) actually uses 4.5 as well. AFAIK OpenGL hasn't changed too much since 3.3, certainly not to the point of being irrelevant for learning.

The shading language has though, so it depends how much one wants to do on the GPU, then again it is kind of irrelevant for beginners.

What approach would you recommend for beginners?

Just follow these tutorials, https://learnopengl.com/

DSA made OpenGL an actually enjoyable interface to work with. Many of my favorite changes(like the 4.5 gl_DrawID) are from later releases.

Maybe 3.3 and 4.5 aren't actually that different, but they certainly feel very different to program.

For me personally DSA was an improvement, but not enough. I wish NV_command_list made it to core one day, amongst other things it introduced a concept of a "state object" which captures all the state and can be easily captured/restored.

I have moved on however towards the DX12/Vulkan like APIs. Currently using WebGPU as a stop-gap, it gives me an easy to use API (compared to Vulkan) with strengths of those explicit APIs. I think in 2021, even if people are writing OpenGL engines, they are already using the "RenderPipeline/RenderPass" abstraction to fit the new APIs better.

OpenGL 4.5 has named objects which makes working with OpenGL feel less archaic. Also 3.3 version doesn't have tessellation shaders. But for some reson OpenGL 3.3 is still being called "a modern OpenGL".

For a while it used to be that OpenGL 3.3 was the only modern version you could guarantee to find everywhere, even on crappy hardware and actually work without major issues.

No idea how it looks like in 2021.

Direct State Access is 4.5 and changes code layout quite a bit

Has the Super Bible superseded the redbook?

I read a second hand copy a long time ago of the red book when it covered the 1.x series, I am starting to have some time to learn graphics programming again and I know that the SuperBible and RedBook were good ones.