I’m running KDE wayland with proprietary Nvidia drivers on CachyOS, so far I haven’t found a way to set a custom monitor refresh rate, on windows I could use the Nvidia control panel to make one (going from 60hz to 75hz). kscreen-doctor doesn’t let you set “unsupported” modes, the kernel launch option of video=1920x1080@75 didn’t work, somehow. So how would I do it?
Are you referring to monitor refresh rate overclocking?
This would not be something you do with a kernel launch option, or DE setting.
You need to be doing stuff with the display server, which would be X11 or Wayland.