I think, I might be wrong, that there's no DHCPd listening. So once you connect the Jolla to the PC, you've got to manually setup the IP for the PC's ethernet.
[nemo@Jolla ~]$ ps aux | grep dhc root 9657 0.0 0.0 1800 496 ? Ss 12:32 0:00 /usr/sbin/udhcpd -f nemo 10488 1.0 0.1 5656 844 pts/0 S+ 13:26 0:00 grep dhc [nemo@Jolla ~]$