I believe the reason why the EC2 linux is not available as an import option with standalone converter is because the import requires the converter to be installed on the EC2 instance.
and the converter standalone comes in .exe.
I have not used this but there is
which has a .tgz download.. Again its something I have not tried, I did not find a doc for open source converter which talks about : Remote Hot Cloning of Powered On Source Machines That Are Running Linux.
there are other options available out there like the VM Import/Export which might help you get the VM back to your on-premises environment