I have a Dell Latitude 6430u dual boot Xubuntu 18.04 and Windows 7
Today I tried upgrading to 20.04 but during the process I got some error messages which said something to the effect that the upgrade did not finish and that the system may be unstable. I took screenshot of those messages (but I cannot access anymore as I left them on my desktop folder) and proceeded to shutdown normally.
Hours later I tried to boot up and I only see a black screen. I can boot into windows 7 without a problem. Next time I try to boot I get something that looks like a command shell and one of the error messages says "Unable to mount root fs on..."
Then I try booting into an older Kernel. It still doesn't work but this seems to get me a little further: I am able to see the Xubuntu logo and the spinning wheel beneath it. But just a black screen afterwards.
I tried booting in recovery mode on an older kernel and do dpkg (repair broken packages) but that didn't seem to fix anything.
Following this post I did sudo apt-get update and sudo apt-get upgrade but I got the following error message: "1407 not fully installed or removed" This was at the same time that it asked me if I wanted to continue. I chose no.
That's where I stand now and I'm out of ideas. I would appreciate any help.