I’m on a 1080 Ti from Evga.
I just tried 470xx but it’s the same effect.
I had to use nvidia-settings because enabling them only in KDE Display settings had/has no effect at all.
I used nvidia-settings to save the config file after editing following this guide to /etc/X11/mhwd.d/nvidia.conf from the manjaro wiki.
I got it working now by using the nouveau drivers but now I run into another very strange issue. As soon as I bump the refresh rate of the third monitor to more than 60 Hz it starts flickering. On my windows I don’t have those problems so I don’t think it’s the cable nor the monitor… I’m very confused here
