The master location for hostname is /storage/.kodi/userdata/addon_data/service.libreelec.settings/oe_settings.xml .. but you'll only see the xml node for hostname if it has been manually added or changed via the GUI. Other services read the hostname from this location to set /etc/hostname (which is a symlink to /storage/.cache/hostname) at boot time.
I just had to change hostnames on several RPis with LE, this wouuld be impossible to guess and nothing normal would work. As usuall, chewitt is right! Thanks for taking the time 
