In this guide, we learn how to upgrade Zorin OS 15 to Zorin OS 16, make sure to get backup of your important data before upgrade, and you will need a bit of patience since the upgrade is big. This is an unofficial way to upgrade your zorin os 15 into zorin os 16 so I’m not recommend using this process with your daily driver pc.
First thing you will need to do is fire up a terminal and type in sudo nautilus. Enter your password and a file manager with admin rights should pop up
Next, go to the root directory of your hard disk and navigate to /etc/apt/sources.list.d/
You will see some files (zorin.list, zorinos-ubuntu-apps-bionic.list, zorinos-ubuntu-drivers-bionic.list and so on.
You need to open those files, look for bionic, and then replace it with focal. If using gedit, use find and replace to replace all bionic with focal. Do this with all 5 files there.
When you have finished that, save them, then open another terminal and type
sudo apt update && sudo apt upgrade -y
Wait for this to finish, restart, and you have updated to zorin os 16