hdmi_edid_file won't work on LE10, this was for the legacy (firmware) graphics drivers. With LE10 you have to use the standard linux kernel KMS approach (as used eg on x86 builds).
The info in our wiki only describes how to do this for x86 builds, on RPi you need to use a slightly different approach:
First dump your edid to the firmware/edid directory, name it eg "myedid.bin":
mkdir -p /storage/.config/firmware/edid
cat /sys/class/drm/card0-HDMI-A-1/edid > /storage/.config/firmware/edid/myedid.bin
Then create a cpio archive so the file is also available in the very early boot stage:
mount -o remount,rw /flash
rm -rf /tmp/cpio
mkdir -p /tmp/cpio/usr/lib/firmware
cp -r /storage/.config/firmware/edid /tmp/cpio/usr/lib/firmware
cd /tmp/cpio
find usr -print | cpio -ov -H newc > /flash/edid.cpio
cd /storage
rm -rf /tmp/cpio
Add the following line to /flash/config.txt to load the edid.cpio as an initramfs
And add the following option to the end of /flash/cmdline.txt (in the same line, separated by a space from the options before) to use your myedid.bin file for the first HDMI port:
drm.edid_firmware=HDMI-A-1:edid/myedid.bin
Then reboot. To verify everything worked fine run "dmesg | grep EDID", you should see the following lines indicating your myedid.bin is used:
LibreELEC:~ # dmesg | grep EDID
[ 3.142571] [drm] Got external EDID base block and 1 extension from "edid/myedid.bin" for connector "HDMI-A-1"
[ 3.153272] [drm] Got external EDID base block and 1 extension from "edid/myedid.bin" for connector "HDMI-A-1"
[ 13.281974] [drm] Got external EDID base block and 1 extension from "edid/myedid.bin" for connector "HDMI-A-1"
[ 17.737414] [drm] Got external EDID base block and 1 extension from "edid/myedid.bin" for connector "HDMI-A-1"
[ 17.751318] [drm] Got external EDID base block and 1 extension from "edid/myedid.bin" for connector "HDMI-A-1"
so long,
Hias