Installing Zorin OS 15.3 Lite Desktop on Ubuntu Server 20.0.4

Would this be possible?

If so what commands would I need to run on Ubuntu Server to install it?

I assume I would have to add the Zorin 15.3 Lite XFCE PPA if one exists?

Zorin os 15.3 is based on Ubuntu 18.04. You would be down grading your server to a previous version of Ubuntu and previous version of the Linux kernel. I would suggest waiting to use Zorin OS 16 lite that is based on Ubuntu 20.04 when available. It would be best to do a fresh install of Zorin OS on your server and backup your data before starting the zorin os 16 lite install.