The Krypton Season 2 premiere opens six months after the events of Season 1.
Trapped in teh Phantom Zone, Seg begins losing his mind as visions from throughout time all assault his senses.
In return, Brainiac and Seg will construct a ship that will take them off the planet and get Seg back home to Krypton.
The fact that Detroit gets bottled means that Brainiac finds some way to escape the Phantom Zone, offering a small hope that perhaps Seg-El can escape as well.