@mrt10001 When the device is unplugged, after holding volume- and power for long enough, it eventually boots into Ubuntu. Sometimes it takes 20 seconds sometimes it takes 60. It never loads the bootloader any more.
EDIT: ok I got it to show up with bootloader for about a second by holding power for 10 seconds as if I was turning it on as usual, then releasing when it vibrates, then volume down and repressing for another 10 seconds. Going to experiment some more.
EDIT 2: for anyone else who ends up with their device in the same state as mine: the trick was to continue holding down both buttons and click on the touch screen while still holding them down, and then I was able to release once it started the bootloader.
Thanks very much for the help! Hopefully I'll be good from here.

are there any carriers that don't have issues with this phone? My 2G and 3G service in my bedroom is only working about half the time.