ZSA Keyboards
From NixOS Wiki
Flashing
ZSA keyboards such as the Ergodox EZ and Moonlander Mark I can be flashed using the keymapp. The command-line tool wally-cli is depricated. The ZSA udev rules can be set up automatically with the hardware.keyboard.zsa config option. In previous versions, your user had to be a member of the plugdev group.
/etc/nixos/configuration.nix
hardware.keyboard.zsa.enable = true;
In addition, you might also want to install keymapp[1]:
/etc/nixos/configuration.nix
environment.systemPackages = with pkgs; [ keymapp ];