Duality does not even activate to summon from extra deck on mobile
Bug reproduction steps
Just try to use the card on any light or dark monster on the field, it’ll not even show the option to activate the card
The card should be a quick effect to activate and tribute the monster under its condition to summon a monster from the extra deck with the different attributes light - dark and vice-versa.
What OS are you using
its an issue with the offline core at this point. An update is coming once we finish making changes to the online core. Should be soon. In the mean time, test online card works fine there. Thanks