I can boot into grub4dos on my laptop with a GPT partitioned SSD by selecting Legacy mode from the Boot Menu (after some fiddling) but I'm not sure what I need to use to boot LibreElec.
I tried:
root (hd0,5)
kernel /KERNEL boot=UUID=LE-BOOT disk=UUID=LE-STORAGE quiet
where LE-BOOT is the label for the FAT32 partition (hd0,5) containing SYSTEM, KERNEL, etc. and LE-STORAGE is the label for the ext3 partition (h0,6).
It starts to boot but then says "error in mount_flash: mount_common: Could not mount UUID=LE-BOOT", so I wonder if the kernel can't recognise the volume labels assigned in Windows (confirmed in BootICE and MiniTool Partition Wizard) or if it's the GPT partitioning that it can't cope with?
I also tried:
root (hd0,5)
kernel /KERNEL boot=sda6 disk=sda7 quiet
but that just gave me "error in mount_flash: mount_part: Unknown filesystem sda6"