copy the original
then edit it theresee, LibreELEC.tv/connman-setup at master · LibreELEC/LibreELEC.tv · GitHub
You have to do this and edit the file like this:
TetheringTechnologies = ethernet
then reboot
and see if a new network interface had come up
ifconfig -a
tether Link encap:Ethernet HWaddr DA:66:BF:DC:0D:CB
inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::98d5:72ff:fe3f:428c%139725136/64 Scope:Link
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:423745 errors:0 dropped:0 overruns:0 frame:0
TX packets:1503562 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0