The answer to how to update the jar file download on Linux is posted in the Sticky post about running Minion on Linux.
Basically,
- change to the Minion directory
- copy the existing jar file and lib directory to a backup directory
- run Minion via terminal command "java -jar Minion-jfx.jar"
- tell it to update (it won't restart)
- copy the new Minion jar file and lib directory from the new "null" directory into the main Minion directory
- restart to the new version