Shortly after that, Zack Snyder commented about the Green Lantern shown in Justice League, saying that was his shot — meaning not a replacement from Joss Whedon or whatnot — but not THE Green Lantern.
Last fall, Zack Snyder confirmed actor Harry Lennix’s DCEU character, General Swanwick, was meant to be revealed in Justice League as secretly Martian Manhunter.
This poster also shows Green Lantern, Darkseid, and Martian Manhunter.
And of course Zack Snyder has shared several images teasing his plans for Darkseid.