Available for PlayStation and Xbox consoles, Digital Cross-Gen Editions include the base game playable on both console generations within the same console family (PlayStation 4 and PlayStation 5 or Xbox One and Xbox Series X|S).
Call of Duty: Modern Warfare II does support crossplay on PlayStation 4, PS5, Xbox One, Xbox Series X, and PC (via Steam and Battle). This means regardless of your platform, you'll be able to play with users on other systems or devices.