If you tell Linux to replace the EDID firmware with a custom binary, without telling it which output to override, I'm not surprised Linux acts the way it does.

If you tell Linux to replace the EDID firmware with a custom binary, without telling it which output to override, I'm not surprised Linux acts the way it does. I can confirm on my machine that overriding EDID for a specific connector works as expected. https://wiki.archlinux.org/title/kernel_mode_setting#Forcing_modes_and_EDID https://wiki.archlinux.org/title/kernel_mode_setting#Forcing... says that you can do it for multiple connectors using commas to separate values, though I have not tried. Though one gotcha is that on my RX 570, `ls -ld /sys/class/drm/*/edid` prints HDMI-A-1 and -2, which is also the name of the display outputs on Wayland, but on X11 xrandr identifies these outputs as HDMI-1 and HDMI-2. (I think you have to use HDMI-A-1 in the kernel command line, but I have not tried.)