JavaFX crashes on Ubuntu 18.04 Linux machines when the XWayland window server is enabled. This happens whenever the FX window toolkit code uses GTK 3 on Linux, which is the default as of JavaFX 11.

The recommended workaround is to use the Xorg server instead of the Wayland server when running JavaFX applications. Note that Wayland is not supported by JDK 10 or JDK 11.

An alternative workaround is to explicitly force GTK 2 by passing the following system property on the command line:

```
    java -Djdk.gtk.version=2 ...
```