Not even sure they can. Of the three god cards, it's the most powerful, and possibly too good for Duel Links since it has protection from targeted effects.
But how often does anybody manage to get something that requires 3 tributes out, especially with cyber style nerfed? And not everything is a target effect. Konami are just being jerks about this. They got people all excited by releasing Slifer right after Ra and made them think Obelisk would be soon after, and now after like, a year, still nothing.
I still think they are being jerks. I have only ever dueled 1 person who was able to get a 3 tribute monster out on me (plasma). And if it started happening all of the time, they could just stop being lazy and learn how to make a card available to use in pve only.