pcloud.nix

{
  inputs = {
    nixpkgs = {
      url = "github:nixos/nixpkgs/nixos-unstable";
    };

    # Recent nixpkgs known to work with pcloud:
    nixpkgs-pcloud-base = {
      url = "github:nixos/nixpkgs/a575c243c23e2851b78c00e9fa245232926ec32f";
    };
  };

  outputs =
    { self
    , nixpkgs
    , nixpkgs-pcloud-base
    }:
    {
      nixosConfigurations = {
        machine =
          let
            nixpkgs-pcloud-base' = import nixpkgs-pcloud-base {
              system = "x86_64-linux";
            };

          in
          nixpkgs.lib.nixosSystem {
            # ...

            modules = [
              # ...

              ({ pkgs, ... }: {
                environment.systemPackages = [
                  (nixpkgs-pcloud-base'.pkgs.pcloud.overrideAttrs (old: {
                    src = pkgs.pcloud.src;
                  }))
                ];
              })
            ];
          };
      };
    };
}