I rebooted it, and after 40m of waiting for network I gave up and flashed it again.
Now, first boot log: http://ix.io/1NEc
I rebooted it now. It will probably take 20 minutes or more for it to become online.
When/if it does, I'll run the armbianmonitor again and update here.
Sadly I don't have a USB -> serial adapter, so if network don't connect I won't be able to run it.
I guess if that happens I can put this on rc.local: sleep 60 && armbianmonitor -u >> someplace
Edit: This wouldn't work, since it uploads to internet, duh. Does it have a parameter to output directly to stdout instead of uploading? (still waiting for the board to boot, so I can't check there)
Update: After the reboot, the network led stays off. It turns on for a few seconds, as usual, and then turns off and stays off. The heartbeat led is flashing as expected.