In April 2015 I started a thread "Wired Network disconnected," because that message had been annoying me almost every time I booted Ubuntu. The end result was that I took Christian's advice to edit connections and delete Wired. That did the trick; I haven't been annoyed by that message since.
Lately I have been trying to get Wi-fi with a USB dongle. It works to the extent that the name of my wi-fi connection, but attempts to really connect have failed after a few seconds. But one thing that has caught my attention is the fact that while trying to connect, the icon up at the top of the screen changes from up-down arrows to the radiating fan-shaped one that used to signal my troublesome wired connection.
It's probably a silly idea, but that made me wonder if perhaps wi-fi is dependent on the wired connection, aka "PA Semi-PWRfficient Gigabit Ethernet," currently listed as "device not managed." I tried to reinstate the deleted Wired connection, but "Wired" is not one of the seven connection types offered.
Meanwhile I got to studying the AmigaONE X1000 Technical Reference Manual again. The Ethernet section mentions a Vitesse VSC8221 Gigabit Ethernet PHY, wired to an RJ45 uplink connector. This caught my attention, because I occasionally get a mysterious message about problems finding "phy." So I opened the box and tracked down those two items.
I noticed that nothing was plugged in to the RJ45 connector. Then I went to the AmigaONE X1000 Quick Start Guide. It said I should connect my Network cable to the RJ45. Mine was plugged into something far below, not sure what. So I replugged my internet cable to the RJ45 as instructed by the Quick Start Guide, rebooted, and YAM and Odyssey could no longer go on line. I switched the cable back to the lower connection.
Color me "puzzleder and puzzleder."