@caganimo123 said in Changing refresh rate manually?:

Can I decouple refresh rate and resolutions and pick them individually? Like 3440x1440 @60Hz

I wonder if you can set a custom mode in /boot/config.txt, something like:

hdmi_cvt=3440 1440 60 6 hdmi_group=2 hdmi_mode=87

If that doesn't work, then I would probably look at booting the Pi from a Raspberry Pi OS card and inspecting the monitor's EDID. From there you may be able to get the raw timings for a custom mode using hdmi_timings=

See

Which values are valid for my monitor? hdmi_timings