I just bought an ultra wide 3440x1440p monitor by LG and tried to use it with my Linux Debian 8. I decided to use Display Port, since HDMI is limited to a maximum frequency of 30 Hertz. Fun fact: While it  perfectly works as long as Gnome is used as desktop environment, it instantly crashes after logging in KDE Plasma (No more output signal)... What is going on? Thanks!
KDE Plasma crashes after logging in
gnome;kde;plasma