The first episode of the Expose The Enemy podcast details Ruby's links to the mafia.
Jon Swinn reads from https://isgp-studies.com/DL_1960s_70s_Jack_Ruby_Tom_Howard_Sam_Giancana_Johnny_Roselli_Jim_Koethe_Bill_Hunter_deaths
Polygraph analysis http://jfkhistory.com/Polygraph/polygraph.html