GNU/Linux Ubuntu 18.04 Installing AMD Open Source Drivers Guide
How to Install AMD Radeon and ATI Open Source Graphics and GPU Drivers in Ubuntu 18.04 Bionic LTS GNU/Linux.
And Open Source AMDGPU Graphics Drivers for Ubuntu Bionic includes Updated Free Graphics Drivers for AMD Graphics Cards.
Especially relevant: as a complement you may be intesested also to the MESA Graphics Drivers Suite Setup.

1. Launching Shell Emulator
Open a Terminal window
Ctrl+Alt+t on desktop
(Press “Enter” to Execute Commands).
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