• On Ubuntu, install the libreoffice-java-common package by calling this command in a terminal:sudo apt-get install libreoffice-java-common
    One problem solved by this is getting a long error message with "NoClassDefFoundError" during installation (see screenshot or like this).
  • On Ubuntu, if you get a message similar to Exception in thread "Thread-402" java.awt.HeadlessException in LibreOffice/OpenOffice, see this stackoverflow answer. Note that the message might not appear in a dialog but only on the command line, so you might want to start LibreOffice/OpenOffice from a terminal window.
  • If you start LibreOffice/OpenOffice from the command line and you get a NoClassDefFoundError, make sure you're not starting LibreOffice/OpenOffice from the LanguageTool installation directory.