Prepare the USB drive using the LibreELEC USB/SD creator like that we know what you get.
Can you try that below also editing the syslinux.cfg in the EFI/BOOT folder but without making any other changes?
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SAY Wait for installer to start or press <TAB> for more options (live, run)
DEFAULT installer
TIMEOUT 50
PROMPT 1LABEL installer
KERNEL /KERNEL
APPEND boot=LABEL=System installer quiet tty vga=currentLABEL live
KERNEL /KERNEL
APPEND boot=LABEL=System live quiet tty vga=currentLABEL run
KERNEL /KERNEL
APPEND boot=LABEL=System disk=LABEL=Storage portable quiet
Are you able to boot the USB now or the problem is that you can't install?