nixos-config/system/app/virtualization.nix

{ config, pkgs, ... }:

{
  environment.systemPackages = with pkgs; [ virt-manager distrobox ];
  virtualisation.libvirtd = {
    allowedBridges = [
      "nm-bridge"
      "virbr0"
    ];
    enable = true;
    qemu.runAsRoot = false;
  };
}