R u running the command using the guake terminal ?
Come over to discord and lets work it out over there.
Yes, I'm using Guake! terminal.
And to your question about running lspci -nnk | grep -iA2 eth, that returns nothing; it just returns to a command prompt and sudo cat /etc/network/interfaces yields:
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
Will head to Discord