Until today i have only been repeating the message from the game's own readme that 16:10 aspect ratio resolutions are not supported. But i never have been able to test myself how it works if you do run the game at it.
DM in a 16:10 aspect ratio, specifically 1920 x 1200. 60 Hz.
All ingame settings for video to the max.
To test i started a new game.
Game fills the screen exactly, and looks great. So far i have no idea what could be a problem, and maybe there isn't any.