Cool project by a guy called Tomasz Mloduchowski:
Raspberry Pi 4 B+ - PCI Express
Seems like it would be easier to use the Jetson Nano if you just wanted to play with PCIE as it has an M.2 connector available. I'm impressed that he got that part off without causing more damage.
I don't think the goal was to play with PCIe. I think that chsllenge was to just see if it could be done on the Pi 4.
