Step-by-step – Radeon Open Source Drivers Ubuntu 18.04 Installation

Installing

2. 2. Enabling AMD Open Source Drivers PPA

   Add AMD Open Source Drivers PPA for Ubuntu GNU/Linux

   Enabling AMD Open Source Drivers Repo for Ubuntu

   AMD Open Source Drivers PPA for Ubuntu

3. 3. Installing AMD Radeon Open Source Drivers

   Then to Install AMDGPU Open Source Graphics Driver for Ubuntu
   First, you are strongly Recommended to Upgrade your System with:

   sudo apt upgrade

   In this case then Reboot:

   sudo reboot

   And to Setup the Amdgpu Driver run:

   sudo apt install xserver-xorg-video-amdgpu

   And for the Legacy ATI Cards possibly:

   sudo apt install xserver-xorg-video-ati

   For further Insight see the Ubuntu Official Radeon Driver Documentation.
   If Got “User is Not in Sudoers file” then Look: Solution
   Finally, to load it reboot with:

   sudo reboot

So Now I’m truly Happy if My Guide could Help you to Install AMD Open Source Drivers on Ubuntu 18.04 Bionic!