apt

If you want to use JavaFX with OpenJDK 8 on Ubuntu you have to install an older version of OpenJFX and its dependencies. sudo apt install openjdk-8-jdk openjfx=8u161-b12-1ubuntu2 libopenjfx-java=8u161-b12-1ubuntu2 libopenjfx-jni=8u161-b12-1ubuntu2 Hold the package, so they wont be upgraded on system updates. sudo apt-mark hold openjfx libopenjfx-java libopenjfx-jni Tested on Ubuntu 18.04.2

One of my main problems while connecting to a serial device was a software called ModemManager which automatically opened a connection to my devices on plug-in. The solution was to disable or remove ModemManager since I never used one of these old dialup modems with my PCs anyways. Remove ModemManager: apt-get purge modemmanager or simply stop it: systemctl stop ModemManager