If you can place 2 ear level in-wall or on-wall speakers at the sides of the seating area, one between the pantry and foyer, second opposite between the patio windows, then you are good for 5.x.4 Atmos.
If not, you could do a 7.1 setup with in-ceiling surround speakers.
Being an open floorplan with mostly reflective walls I would strongly consider ditching the entertainment center idea for a clean stretch fabric look with recessed TV and speakers behind the fabric. Use directional speakers and fill the area behind with sound absorbing material.
For in-ceiling speakers look for ones with angled baffle, 30-40deg is ideal. Place them 35-45 deg behind and in front of the listening area.