The Alfa Romeo team have fitted their C38 with a set of additional fins on the upper edges of the monocoque. Attached to the panel that covers the upper front suspension elements, there are 4 vertical fins on the left and right sides of the S-duct exit.
Just like the fins that Mercedes added, they direct airflow outboard, helping extraction of air out of the S-duct.
The image also reveals how the panel isn't really a great fit onto the monocoque, and even worse so against the nose cone. There is quite a visible ridge that the team will probably be looking into to further improve efficiency.
Also note how the C38 features a front suspension with a separate steering arm. Where most teams are lining up the steering arm behind the lower front wishbone, or even mount it inside the wishbone shroud, but Alfa opted not to. It obviously remains speculation as to why, but it may be for aerodynamic reasons, or packaging inside the monocoque.