It's not the right tool for the job. OP is specifically asking about automating installs of UBUNTU, and here you come with this pushy nonsense. OP needs to know how to do something, not what your personal favorite little thing is.
Lastly, Nix and Guix are for bit-level accuracy on install, not AUTOMATED installs. The ability to have reproducible results is for accuracy, not automation. It doesn't solve the very probably they were asking about.
You have zero idea what you are even doing in this thread, or what you're talking about.