os/modules/core/fonts.nix

{
  config,
  pkgs,
  lib,
  ...
}: {
  fonts = {
    fonts = with pkgs; [powerline-fonts dejavu_fonts];
    fontconfig.defaultFonts = {
      monospace = ["DejaVu Sans Mono for Powerline"];
      sansSerif = ["DejaVu Sans"];
    };
  };
}