DARKEST DAYS is now available on Steam as a free-to-play release, which is apparently part of a Global Open Beta for the Zombie Apocalypse Game. This game from Korean developer NHN started on mobiles. The beta supports crossplay, and this post has a cross-platform usage guide. Unfortunately, early reviews are pretty savage, criticizing the port and its pay-to-win mechanics. Here's a recent Gameplay Teaser Trailer and here are the details:
DARKEST DAYS is a zombie shooting RPG set in a post-apocalyptic world devastated by a sudden zombie outbreak. Explore a dark yet captivating open world, build a sanctuary with fellow survivors, grow stronger, and fight for survival.