Kodi "Matrix" 19.4: more bug fixes, some backports, no real new features.
There are no major changes since the previous version, and you should be fine to install over the top of any existing Kodi 19.x installation.
For Ubuntu, enter the following commands. Follow the prompts as you would any other software installation.
sudo apt install software-properties-common sudo add-apt-repository -y ppa:team-xbmc/ppa sudo apt install kodi