I'm trying to upgrade my system from 18.04 to 20.04 using update-manager. No matter what I seem to try, I get an error while calculating the upgrade:
Could not calculate the upgrade An unresolvable problem occurred while calculating the upgrade.
At first, the error gave me a reason: I had to purge all Launchpad PPAs. I did that, and after still receiving the same error, I did some searching and found this bug report where some users said installing clang-9 solved this issue. I did so myself, and now I get the same error with a different explanation: I've "installed a prerelease version. This is a transient issue." So I removed clang-9, updated and autoremoved everything, and now I just get the error without any suggested explanation at all.
Since this dialogue isn't helping, I trekked on over to my /var/log/dist-upgrade/main.log, where I saw this line:
ERROR Dist-upgrade failed: 'E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.'
I then checked apt.log to see what was going on. There is clearly quite a bit going wrong.
What are my options from here? If you grep this log for "Broken," there are quite a few packages that the upgrader views as broken (though none of them show up with dpkg or in Synaptic), and removing all of them is unfeasible and I worry may break my whole system. Based on the list of problem packages, I'm thinking there exists a key package or two that fixing will eliminate the whole issue. I am just not sure which ones they might be. Any help would be greatly appreciated.