The on-board ethernet is not recognized by any version of Ubuntu server. I have tried UBuntu 18.04 LTS, 18.10, 19.04 and 19.10 and they all fail to recognize the ethernet.
What model ethernet is used for this NUC and how can I get Ubuntu to install and recognize the ethernet?
Only Windows 10 is supported on your NUC:
You can find the adapter information here:
Lan: Intel® Ethernet Connection I219-V
WiFi: Intel® Wireless-AX MAC
While the i219-V is a PHY that has been around for a while, the MAC in the chipset used in the FN NUCs is probably new, likely with differing PCI Ids, and (thus) is not recognized by the version of the driver in these releases of Ubuntu. You will have to wait for an update to Ubuntu that delivers a driver supporting this MAC.
In the meantime, a USB Ethernet dongle may be your only workaround. These are pretty cheap; I see units with USB 3.0 and Gigabit support on Amazon for as low as US$7.