I have a 4K monitor capable of 60 Hz with HDMI 2.
I have it connected to my machine with the 60Hz-capable cable that came with the monitor.
However, in the Display options of KDE the highest Refresh rate is 30.00 Hz, and not 60 Hz (it's currently set to auto). The display options display that it's using HDMI 1, and not HDMI 2.
I also looked through all the settings of my monitor.
I currently don't have a graphics card installed, mainly because my graphics card doesn't seem to really work with free graphics card divers (the nouveau driver in my case) even though it looks like it should according to a website about nouveau. I'm running latest Debian10 with KDE.
Maybe the cvt or xrandr commands could be used for this somehow - if so: how to know which? And if 60 Hz support can be added why is configuring it not an option in the KDE settings?