It's possible to find the WSL version from inside the distro like this

strings /init | sed -nE 's/.* container_host_version_id=(.+\..+\..+\..+)/\1/p'

We might be able to use that to issue a warning on old WSL versions

On a different topic, my own question.
https://nix-community.github.io/NixOS-WSL/how-to/nix-flakes.html
Mentions to "First add a nixos-wsl input, then add nixos-wsl.nixosModules.default to your nixos configuration."
I assume by "nixos configuration" it means configuration.nix.
But how exactly do I add nixos-wsl.nixosModules.default to it. Say to the base configuration.nix that comes with nixOS WSL of:

# your system. Help is available in the configuration.nix(5) man page, on
# https://search.nixos.org/options and in the NixOS manual (`nixos-help`).

# NixOS-WSL specific options are documented on the NixOS-WSL repository:
# https://github.com/nix-community/NixOS-WSL

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

{
  imports = [
    # include NixOS-WSL modules
    <nixos-wsl/modules>
    nixos-wsl.nixosModules.default
  ];

  wsl.enable = true;
  wsl.defaultUser = "nixos";
  

  # This value determines the NixOS release from which the default
  # settings for stateful data, like file locations and database versions
  # on your system were taken. It's perfectly fine and recommended to leave
  # this value at the release version of the first install of this system.
  # Before changing this value read the documentation for this option
  # (e.g. man configuration.nix or on https://nixos.org/nixos/options.html).
  system.stateVersion = "24.05"; # Did you read the comment?
}

Ive googled a bunch and used the current best coding AI Claude 3.7 sonnet with no luck.