This might be a stupid question but if someone wants to start with some basic GPU to get an an understanding of how these things work, what that GPU would be that's wide spread, not that archaic?
IMO, writing some Vulkan (it being a thin layer over what a modern GPU's "actually" doing) would be good to get fundamentals down first, not the least of which because you'll have the validation layers to yell at you for incorrect usage instead of getting mysterious GPU behavior.