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.
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.
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"
How to fix Flickering in some versions of Linux on VirtualBox