If you're using nix, I was able to make a build from the darktable derivation[0] modified to use fetchgit (since he hasn't made a github Release since December) and `s/darktable/ansel/g`.

    src = fetchgit {
      url = "https://github.com/aurelienpierreeng/ansel.git";
      rev    = "f7669af89a71882ebad15982d698b8df7e6c6ce8";
      sha256 = "sha256-FI6dKUrmtTG7DIV0MmY6XdqlUpqdt7boKuXKU6CywjA=";
      fetchSubmodules = true;
    };

[0] https://github.com/NixOS/nixpkgs/blob/nixpkgs-unstable/pkgs/...