VirtualBox: How to fix screen flickering on Ubuntu 20.04

Screen flickering and multiple keyboard input events are very annoying. I have solved both issues on Ubuntu 20.04 that is running as guest virtual machine in VirtualBox 6.1 on macOS Big Sur 11.1.

VirtualBox: Screen flickering on Ubuntu 20.04
VirtualBox: Screen flickering on Ubuntu 20.04

When I tried to log in to the guest operating system Ubuntu 20.04 the screen flickered and keyboard events were interpreted several times on the login screen. For example, the entered password “Ubuntu” was interpreted as “UUUbbb…”.

Thanks to the blog post “How to fix Flickering in some versions of Linux on VirtualBox” I have solved the issues. It seems that those problems occur on Linux systems which run as guest virtual machine in VirtualBox on macOS.

Disable Wayland

Both problems are permanently fixed when “Wayland” is disabled.

# Depending on your preference you can use 'gedit' or 'vi'
sudo vi /etc/gdm3/custom.conf

# Uncomment "WaylandEnable=false"
Ubuntu 20.04: Disable Wayland
Ubuntu 20.04: Disable Wayland

Tip for a minimal installation of Ubuntu (Update: 10.03.2021)

If you only set up Ubuntu in the mode “Minimal Installation”, then you need to install GCC for compiling perl modules. This is required for installing the Guest Additions of VirtualBox.

sudo apt install gcc perl make

Only after you installed the Guest Additions the flickering will stop.

VirtualBox Settings (Update: 10.03.2021)

These are my settings:

System: 
  Base Memory: 4GB
  Extended Features: Enable I/O APIC and Hardware Clock in UTC Time
  Processor: More than one
  Execution Cap: 100%
  Paravirtualization Interface: Default
  Hardware Virtualization: Enable Nested Paging
Display:
  Video Memory: 128 MB
  Monitor Count: 1
  Scale Factor: 100%
  Graphic Controller: VBoxSVGA
  Acceleration: Disabled
Network:
  Enable Network Adapter: Attached to Bridged Adapter

Further information:
How to fix Flickering in some versions of Linux on VirtualBox

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