ZSA Keyboards
From NixOS Wiki
Flashing
ZSA keyboards such as the Ergodox EZ, Moonlander, and Voyager can be flashed using the GUI app Keymapp. The ZSA udev rules can be set up automatically with the hardware.keyboard.zsa config option.
/etc/nixos/configuration.nix
hardware.keyboard.zsa.enable = true;
In addition, you can install Keymapp itself with:
/etc/nixos/configuration.nix
environment.systemPackages = with pkgs; [ keymapp ];