The EcoSport is new for 2018. It has a narrow center that does not fit even a narrow booster, and rigid buckles for all 3 seats. This back seat is not one that will do well for 2 side-by-side or 3-across.
The innermost lower anchors (belonging to the side seats) are spaced 15.8 inches apart and may be borrowed to install a car seat in the center so long as the car seat manufacturer is OK with this wider spacing (standard spacing is 11 inches). See here for more about which car seats are OK with a wider spacing for the lower anchors.
