Download file could be corrupt? Here's the MD5sum of the image that just worked on my 4b: 7655db033c7a2f56bfe1adb2733fb8c1 LibreELEC-RPi4.arm-9.2.0.img.gz
I was having the same issue, but just downloaded the latest image and everything worked. Image was copied direct to flash card via '# gzip -dc LibreELEC-RPi4.arm-9.2.0.img.gz > /dev/sdX && sync'.