Howdy there, I am Robert, nice to meet you. Sorry about the Linux set up being rather confusing we've simplified the Windows version recently and I am trying to simplify the Linux set up as well. This is why I created this page to explain these packages recently and added it to the download page.
http://enigma-dev.org/docs/Wiki/Install:Extra_PackagesThese packages were also outdated in the install.py script for some time until yesterday when I finally updated them. Basically JNA is just to be able to use dll's and .so's in Java which we need because we link our compiler as a library, and it goes in enigma-dev/plugins/shared if you look at the announcements page I also made a topic recently about us updating to JNA 4 for ARM. Now the plugin enigma.jar goes under enigma-dev/plugins/ and is detected along with any other plugin jars people want to write when LGM loads, during the splash screen. LateralGM itself should just go under enigma-dev/ though as that is where install.py places it.
Did you run the python installation script?