It's FOSS - https://itsfoss.com/install-xfce-desktop-xubuntu/
Brief: You’ll learn how to install Xfce desktop on Ubuntu. You’ll also learn how to convert your Ubuntu desktop into Xubuntu desktop. Yes, there is a difference between installing Xfce and Xubuntu desktop.
One of the various ways to speed up Ubuntu is to use a lightweight desktop environment as it consumes fewer system resources. If you weren’t sure which Ubuntu to use and opted for the default Ubuntu, you may feel like using another desktop environment that better suits your need.
The good thing about Linux is that you can install another desktop environment (DE) along with your current