Puppet Master must be protected well. It is a high-risk asset. With Puppet, you can install software on all your servers and clients. Puppet agents on Linux and Windows run with root and admin rights respectively. Think about a scenario where a hacker gets control of it. He can easily run any command, install backdoors, and fully compromise your IT infrastructure.
I suggest using the Ubuntu Server version that does not have a graphical user interface. This will ensure that there will not be much unnecessary software on your Puppet Master. Having only the necessary software on it helps you to have a more secure server, and also to keep the performance higher.
Do not install any software that is not necessary. ...