Ideally you need to update to a later version of the Unity engine, so Linux gamers don't have to do this :)
To address fullscreen issue on Linux, you can also edit
$HOME/.config/unity3d/Droog71/Redshift 7/prefs
And set there:
<pref name="Screenmanager Is Fullscreen mode" type="int">0</pref>
Then just turn the game fullscreen with your window manager shortcut (F11 in KDE for example).
Hello. The current build of Redshift 7 was made using Unity 2017.1.0f3. The bug is not present with Ubuntu but does occur with Debian 9. I think that maybe the bug with Unity was never completely fixed for all operating systems.