Three suggestions that might work:
a) Enable "legacy boot" in BIOS settings which should disable EFI boot.
b) Boot from any other Linux distro USB and run "dd if=/path/to/LibreELEC-Generic.x86_64-9.0.2.img of=/dev/sda bs=1M" (checking the disk you want to write to is /dev/sda .. and noting the image is uncompressed to .img not .img.gz). This writes the USB image to the HDD, and in theory this should boot, time out the same way, but this time it self-installs to the HDD not the USB so you end up with a working install.
c) Remove the HDD and put it in a USB caddy to write the image to the HDD .. different way to the same result as B.
A is easier than B which is marginally more complex but requires no extra hardware like C