In the far future, after the galaxy has been torn asunder by the Age Of Strife, The God Emperor of Mankind searches for his lost sons, stolen from him by the Ruinous Powers of Chaos.

To his surprise, the Emperor gradually discovers that all of his sons have been replaced by duplicates of Clark Kent/Kal-El, a humanoid looking xeno who once protected a parallel reality version of Ancient Terra.

The Emperor gazes into this xeno's mind and sees that he is pure of heart, strong of will, and untainted by chaos. Though he is disappointed to have lost his sons, and suspicious of where they may be, the Emperor decides to make use of what he has. The human race must endure!

Can twenty clones of Superman protect the 30k galaxy, and prevent it from going to pot like the Primarchs did?

Every duplicate of Supes all have the same memories, thoughts, emotions, values, etc as one another. They are unfamiliar with this galaxy, nevertheless they still want to do everything to protect the inhabitants and create a decent life for them all. They still believe in truth, justice, and the American way/a better tomorrow despite how grimdark everything is.