interesting, you have a link to the EK cargo starting in Sep ?
I can think of a few over the years that are missing who were regular visitor to STN not sure if they had a Scheduled operation or not
Volga Dneper
Heavylift
Atlas Air
Swaziland Air cargo
TNT
Titan ( Royal mail service )
Martinair cargo
British world airlines / British air ferries
Cygnus Air /Air swift
Emerald airways
According to the Stansted website
KLM , Egypt Air , Antanov airlines and Etihad still operate cargo flights to STN
https://www.stanstedairport.com/about-us/cargo/