blackride The bootloader is unable to find a partition with the label "LIBREELEC" to load the SYSTEM file. It has nothing to do with the device-tree being used. The LIBREELEC label is used with the FAT16/VFAT partition on the .img file we use for imaging SD cards and eMMC modules for the C2 board and the configuation is defined in extlinux.conf where we set boot=LABEL=LIBREELEC and disk=LABEL=STORAGE. If you have swapped between Olegs images (which used non-standard u-boot bootscripts and locations/naming sometimes) and mine or LE10 nightlies the extlinux.conf might be wrong (see if UUID or /dev/device works instead of LABEL). Sometimes sudden power-off without shutdown will result in card corruption; normally fixable with fsck. It's hard to comment without knowing the history of the device, e.g. what was originally installed, from where, and when, and what update was performed.
NB: I've run boot tests with LibreELEC-AMLGX.arm-10.0.0-odroid-c2.img.gz on SD card and an eMMC module and (from a boot/install/run perspectice) the image works fine for me.