I've tried to upgrade 19.04 to 19.10. Now when I start the system, it loads, but is not usable as the only thing I see is "Oh no! Something has gone wrong". I can see activities though and there are "Sorry, Ubuntu 19.10 has experienced an internal error" and "System program problem detected" windows, but I can't get to them -- it goes back to "Oh no!" window.
Upgrade process was not smooth. At some point the messages were displayed:
lvm2-activation-generator: lvmconfig failed lvm2-activation-generator: Activation generator failed.
I fixed this problem, following this advice: Kernel Panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
This is similar problem, but for me disabling autologin hasn't helped: Unable to login after upgrading to 19.10 from 19.04