In order to avoid spamming the card members with notifications whenever Elegantt calculates its estimated end date, we chose to use a custom due date rather than the one used by Trello.
It actually does have some drawbacks, such as the fact that due dates don't automatically appear in the calendar view.
That being said, you are able to create a Trello native due date at the same time than your Elegantt due date, by ticking on "Add a Due date":
