What are the requirements to get to battle the devs? I basically did all post game story besides going to the Battle Frontier. Do I have to do something there?
Use the emolga taxi and soar to dev island, near Selene City.
Just use your dexnav from the menu and press the pokeball on the right with the mouse.Then close the menu and try to walk.A list with all devs should appear giving you the option to choose whoever you want to battle.Hope i helped 
Oh. Thats why. I despise soaring because I can’t even land the thing and then I have to load a backup save. How do I land it?
Confirm on top of something like a pokemon center or in the dev island’s case, the tower.