It's been a while since I dove headfirst into a milsim, but Offworld Industries' bid to revitalize its WW2 spinoff of Squad makes me want to clear my calendar. Post Scriptum (2018) has been fully acquired by publisher and Squad developer Offworld Industries, who's slapped on a new label that better reflects what you're getting: Squad, but set in 1944.
But it's also been substantially updated. A huge patch yesterday added two new factions (the Greeks and Aussies), a map, seven weapons, and a bunch of balancing changes.