proper hack, works without disko too

{
  config,
  pkgs,
  lib,
  ...
}:

let
  installBootLoader =
    (import (pkgs.path + "/nixos/modules/system/boot/loader/generic-extlinux-compatible") {
      inherit config lib pkgs;
    }).config.content.system.build.installBootLoader;

  populateFirmware =
    (import (pkgs.path + "/nixos/modules/installer/sd-card/sd-image-aarch64.nix") {
      inherit config lib pkgs;
    }).sdImage.populateFirmwareCommands;

  installCommand = pkgs.writeShellScript "populate-boot.sh" ''
    set -e && export PATH=${pkgs.coreutils}/bin:$PATH
    ${builtins.replaceStrings [ "firmware/" ] [ "boot/" ] populateFirmware}
    echo "include usercfg.txt" >> boot/config.txt
    ${installBootLoader} "$@"
  '';
in
{
  system.build.installBootLoader = lib.mkForce installCommand;
}

How do you guys handle diffrent /dev/* paths,

i use nixos anywhere to add nodes to my cluster but some nodes will have /dev/nvme0n1 as root and some /dev/sda1 and so on

Is there way to automatically select which ever is avaialable ?