Unable to play the file / Missing decoder on Ubuntu 20.04 LTS Focal Fossa - LinuxConfig.org

In this tutorial you will learn how to install all commonly used media codecs and fonts for Ubuntu 20.04 LTS Focal Fossa. By default when you attempt to play multimedia file using the default media player the error message appears stating that the video or audio player is unable to play file due the the missing decoder.
This is a companion discussion topic for the original entry at https://linuxconfig.org/unable-to-play-the-file-missing-decoder-on-ubuntu-20-04-lts-focal-fossa