For LISA 7.5.1, the SSH step is an out of the box feature available after a custom extension is placed in the hot deploy folder.
This custom extension was already available, but the connection testing was failing with the message "Connection Test Failed".
The Workstation log file had the following information:

DEBUG com.itko.lisa.ext.ssh - ***** Unable to borrow object 
WARN com.itko.lisa.test.LisaException - LisaException detail There was a problem while connecting to <hostname>:22 exception is java.io.IOException: There was a problem while connecting to <hostname>:22 
DEBUG com.itko.lisa.ext.ssh - Invalidating connection for: <username>@<hostname>:Authenticate with Keyboard Interactive 
DEBUG com.itko.lisa.ext.ssh - null 
java.lang.NullPointerException 
at com.itko.lisa.ext.trilead.TrileadConnectionFactory.cleanupConnection(TrileadConnectionFactory.java:121) 
at com.itko.lisa.ext.trilead.SSHStepEditor$7.doCallback(SSHStepEditor.java:313) 
at com.itko.util.swing.panels.ProcessingDialog$2.run(ProcessingDialog.java:194) 
at java.lang.Thread.run(Unknown Source) 

LISA on release 7.5.1

Replace the previous custom jar files with the ones available in the following community thread:
https://communities.ca.com/thread/241739216