How can I install nixops?

I’ve gotten a VPS at vpsfree and they instruct me to get nixops to be able to deploy, but all I find in nixpkgs is nixops_unstable, which doesn’t build

building Nix...
building the system configuration...
error: Package ‘python3.10-requests-2.28.2’ in /nix/store/56727vjqg650ixvq84p7xrwwh93a7cma-nixos-23.05/nixos/pkgs/development/tools/poetry2nix/poetry2nix/pkgs/poetry/poetry.lock:0 is marked as insecure, refusing to evaluate.

       Known issues:
        - CVE-2023-32681

       You can install it anyway by allowing this package, using the
       following methods:

       a) To temporarily allow all insecure packages, you can use an environment
          variable for a single invocation of the nix tools:

            $ export NIXPKGS_ALLOW_INSECURE=1

        Note: For `nix shell`, `nix build`, `nix develop` or any other Nix 2.4+
        (Flake) command, `--impure` must be passed in order to read this
        environment variable.

       b) for `nixos-rebuild` you can add ‘python3.10-requests-2.28.2’ to
          `nixpkgs.config.permittedInsecurePackages` in the configuration.nix,
          like so:

              nixpkgs.config.permittedInsecurePackages = [

       c) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
          ‘python3.10-requests-2.28.2’ to `permittedInsecurePackages` in
          ~/.config/nixpkgs/config.nix, like so:

              permittedInsecurePackages = [
(use '--show-trace' to show detailed location information)

Did you do what the message says?

Good question;). I think what I really wanted to ask was:

Why is there no nixops and only nixops_unstable? Isn’t nixops the oldest of the bunch and yet I have to install an insecure version?

Nixops v1 relied on Python 2 and various old and increasingly broken dependencies, and so was removed in treewide: drop poetry2nix by K900 · Pull Request #263308 · NixOS/nixpkgs · GitHub.

Older projects often get less maintenance, so it’s more like and therefore you have to install an insecure version.