Install VirtualBox on Ubuntu 20.04 Focal Fossa Linux -

The objective of this tutorial is to install VirtualBox on Ubuntu 20.04 Focal Fossa Linux. VirtualBox is a free and open-source hosted hypervisor for x86 virtualization, developed and maintained by Oracle Corporation.
This is a companion discussion topic for the original entry at

I have a severe problem with virtualbox running under ubuntu 20.04. the remote display does not work, even if i install the extension pack. when running under ubuntu 18.04 and earlier the remote display works. as the remote display is essential for me, this is the reason not to update to ubuntu 20.04 until i find a solution. or do you have an idea how to fox it?