Can't run ETX after upgrade to nixos-22.11

I have to use the Exceed TurboX client to access a remote desktop. It uses a proprietary binary launcher called from a browser web interface. The launcher downloads the etxc binary client program to establish a connection to a remote desktop.

In nixos-22.05 I was using buildFHSUserEnv in flake and everything did work

  description = "Packages for using OpenText Exceed TurboX";

  inputs = {
    # nixpkgs.url = github:NixOS/nixpkgs/f09ad462c5a121d0239fde645aacb2221553a217;
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.11";

  outputs = { self, nixpkgs }:

      callPackageUnfree = pkg:
        with import nixpkgs {
          system = "x86_64-linux";
          config.allowUnfree = true;
        }; callPackage pkg;
    in rec {

      packages.x86_64-linux.etx-launcher =
        callPackageUnfree ./pkgs/applications/networking/remote/etx-launcher { };

      defaultPackage.x86_64-linux = packages.x86_64-linux.etx-launcher;

      etxEnv = with import nixpkgs { system = "x86_64-linux"; };
        pkgs.buildFHSUserEnv {
          name = "etx-env";
          targetPkgs = pkgs: (with pkgs;
            [ gdk-pixbuf
            ]) ++ (with pkgs.xorg;
              [ libX11
          runScript = "bash";
          # runScript = "${firefox}/bin/firefox";

      apps.x86_64-linux.default = {
        type = "app";
        program = "${self.etxEnv}/bin/${}";

Unfortunately this doesn’t work anymore after upgrading to nixos-22.11, neither with the original hash, nor after upgrading to the latest nixos-22.11. The launcher is started, but the desktop never appears and I see no error messages. ldd suggests that all libraries are bound by both the launcher and the etxc binary. I’ve tried to replace the etxc binary with a script wrapping it in strace but it detects that the binary is not the expected one.

I would be great for any suggestion on ways to further debug this.