Was initially able to launch the game, but had only sound and a taskbar icon, no game screen would appear. Had to alter a configuration file 'options4.txt': changed Fullscreen from 0 to 1. On my system, this file is kept at: ~/.local/share/Steam/steamapps/compatdata/1845670/pfx/drive_c/users/steamuser/AppData/Local/Islands_of_the_Caliph Once this was changed the game worked flawlessly.