I traced this problem to RXTXCommDriver.java:415: System.getProperty("java.ext.dirs") comes back null. It's illegal to -Djava.ext.dirs on Java 10/11. The easiest fix appears to be to add a second argument (default value) of the empty string, which makes the code/loop a noop. That, or try and switch it over to classpath? It's unclear to me where it's expecting to find a property file file, but maybe it does in some setups.
Debugging is a lot easier if you add e.printStackTrace(); to all three /thrown while loading/ catch and discard blocks. Also, the package fails to build for me on Ubuntu's Java "11" (i.e. Java 10 in a weird package name), due to javah removal. Chris.