Justice League: The Darkseid War
Steppenwolf returns to Apokolips via boom tube - to Darkseid's feet. Before his groveling can even begin, he's killed by omega beams. He takes a very brief look through the tube to see a triumphant Justice League - taking quick note of the planet he's about to invade before the portal closes.
The Flash and Superman are finishing their race. With Kent in the lead, Allen turns on the afterburners, unknowingly opening up a time rift via the Speed Force. He ends up in the reality that Bruce Wayne envisioned in Dawn of Justice. It reaches a point in which he encounters Dark Superman. He recognizes Allen as a man he knows is dead, and chases him across the globe, where another rift is exploited. After entering a new and worse reality, he realizes how and why this is happening, and eventually sends the message to Batman as seen before. After the deed is done, he returns to a familiar world, with an unfamiliar and youthful Batman (and a long-retired Bruce Wayne).
Wonder Woman returns to Themyscira to learn more about the war with Uxas - discovering that Steppenwolf is only the beginning to a bigger threat. She prays to gods that no longer exist, training to hone and perfect her New God powers, and leaves with nothing but advice and a heed to stay away from the island to honor the Queen and keep them off of the modern radar.
Aquaman receives a visit from the Martian Manhunter. A legend known to the Atlanteans. Familiar with Steppenwolf and Uxas, he warns of the coming danger. Arthur requests his brother's help in defending the world, which he declines, because of his spite for the walkers and his thought that Darkseid will not threaten the oceans. Upon returning to the surface, he's transforms into General Swanwick.
Batman does some Mother Box stuff with Cyborg under the Hall of Justice. A couple of Green Lanterns (Jordan and Stewart) show up. Shazam shows up. hits the fan. Alexander Luthor forms an Injustice League. I got bored after that last paragraph.