Yes. I have briefly encountered the real coffee nerds. They are extremely serious and meticulous about their coffee, do actual science, and, I am sad to say, the coffee was better than any coffee I have had before or since.

You will not get coffee that good from a coffee shop, it isn't economically viable. But the technology exists.

Arguably for "coffee geeks" it is a hobby!

I'd assume the coffee geeks have figured out how to make cheaper machines and put the designs on github.

They have, kind of. Check out Gaggiuino. Sadly not really open source (Gen3) but you can get a cheap $500 Gaggia Classic and add fine grained control with an Arduino and display: https://gaggiuino.github.io

Then there's the really open source Rancilio PID Clever coffee project:

https://github.com/rancilio-pid/clevercoffee

Different machine, similar approach, a bit more DIY since you can't buy a kit.