Another option is to find a Nixpkgs commit which does contain the version of a package that you want. You can pin and import it as a Flake input, and use the ol

Another option is to find a Nixpkgs commit which does contain the version of a package that you want. You can pin and import it as a Flake input, and use the old version of the package provided. So in its own way, Nix and Nixpkgs do serve the purpose of software preservation, as long as you have the full commit history for Nixpkgs. Preservation doesn't imply maintenance however. It's fair for Nixpkgs to delete packages that are no longer supported, as that's a burden on the limited number of maintainers. By recreating the package and module in my own Flake, I've taken on responsibility for maintaining it myself, and not adding any work to the Nixpkgs maintainers. NixOS modules in particular aren't easy to extend, so I ended up copying it entirely. And to be honest, the thought of using an old version of Nixpkgs didn't cross my mind while setting up syncserver. Hopefully it's easier to maintain with poetry2nix now that I've got the package working.