Hello,
I open a new thread in LibreNMS forum to support CoreELEC SNMP temperature: https://community.librenms.org/t/add-temperature-for-coreelec-devices/11248
It will be great to have a official support for CoreELEC devices, something similar to Raspberry Pi: https://raw.githubusercontent.com/librenms/librenms-agent/master/snmp/raspberry.sh
Regards.