Dentro do ZIP, tem o arquivo Install.txt que te dá as o passo a passo para a instalação:
Linux
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Choose your binary build - x86_64 or i386 (based on which version of
the JVM you are installing to)
NOTE: You MUST match your architecture. You can't install the i386
version on a 64-bit version of the JDK and vice-versa.
For a JDK installation on architecture=i386
Copy RXTXcomm.jar ---> <JAVA_HOME>/jre/lib/ext
Copy librxtxSerial.so ---> <JAVA_HOME>/jre/lib/i386/
Copy librxtxParallel.so ---> <JAVA_HOME>/jre/lib/i386/
NOTE: For a JDK installation on architecture=x86_64, just change the
i386 to x86_64 above.