I'm really frustrated from trying to get spi to work on the 
#RaspberryPi Zero with 
#NixOS 😔
I don't understand this device-tree stuff and no matter what I do, no /dev/spi* will appear. Also nothing in nixos-hardware unfortunately.
If anyone can offer to help, I am starting to be willing to throw money at the problem 🙃
@nobodyinperson I don't think you need to mess up with the device tree. Normally not. But I don't know NixOS.
Did you try to put dtparam=spi=on at your /boot/config.txt?
@nobodyinperson Also, can you check if spi driver is loaded?
sudo lsmod | grep spi
If not, you can try to:
sudo modprobe spi-bcm2835
If it works you can add it to module.d to load with the system.
Yann Büchau 
OTA