I think I may have some further insight. I tried arch and remix os today and same thing happens with the ethernet cable connected. It looks like other people with 2GB boards are having the same problem (e.g. look here: http://forum.pine64.org/showthread.php?tid=488).
[edit] plugging in the ethernet after booting up remix os causes an instant crash followed by endless bootloop
[edit 2] just tried arch - the exact thing happens as with Ubuntu
[edit] plugging in the ethernet after booting up remix os causes an instant crash followed by endless bootloop
[edit 2] just tried arch - the exact thing happens as with Ubuntu