I have a Raspberry Pi 4 and it’s plugged into an ultrawide monitor because that’s the only monitor I have which has any HDMI ports. I know that the Pi doesn’t have a resolution option for 2560 * 1080 but I don’t think that would cause no display output, as I have previously managed to get a display output on this monitor.
I have tried the suggestions on the Raspberry Pi forums, such as setting the
hdmi_hotplug option, but no dice. I still sometimes get no display output and the only solution (which is not ideal) seems to be to reboot the Pi. I have not tested with another monitor because I do not have another HDMI-capable monitor.