My setup on Ubuntu, my displays are primary 1920 x 1080 and Secondary 1200 x 1920 (portrait mode). The game no matter what I do launches on the secondary display in 1920 x 1080 and being as it is a portrait display I can only see a slither of the game screen. I cant even read the setting menu because it off the side of the 1200 wide portrait screen.
I now have close to a dozen linux steam games and this is the only one that insists on launching on a secondary monitor.
I've reinstalled the game. Reinstalled Ubuntu 14.04 / 15.04 and are now on 15.10. Same problem everytime.
This has been the case for me since beta. I just gave up on the game and check sometimes when I feel like playing and its still broken.
Customer support service by UserEcho