[2021] Is there a quest to sell the main building of the elemental section?

@elvenprincess2 are you talking about the portal of your settlement?  

@elvenprincess2 please make a ticket to support  

Furthermore, I want to add something:

Do not worry very much about portal-selling quests. If you need to sell your portal, do it. If you get the quest, and your portal is gone, any portal is good. You can build anywhere the little 2x2 dwarven portal and then sell it. It will cash the quest!