John Henry shares details about his doppelgänger with Clark & Lois 

The character we know as John Henry Irons was established since season 1 as someone from another universe. So it makes sense for there to be a John Henry Irons from this universe, who was confirmed to be killed at the end of season 2 by John Diggle.

Everyone has a Dopplerganger. This Superman is a doppleganger of earth prime Superman an vice versa.

Yeah he was killed by Bruno Mannheim and Onamonatopoeia

During Superman interrogation of John Henry Irons in the first season it was revealed that his doggelganger died of unusual circumstances.

​@@stephennguyen6124 Not everybody. But it has been mentioned multiple times on this show that John Henry Irons had a dobbelgagger.