The new binary path is at Engine/Binaries/Linux/FactoryServer-Linux-Shipping. It needs to be updated or it doesn't run.
Thanks for writing this script btw.
I made an updated version here also with some new options, I can make a PR if u want:
https://github.com/fjij/nix-configs/blob/de27bce02f1e0b7fd754d21764a5087899471c4f/nixos-modules/satisfactory.nix