Could not calculate the upgrade - An unresolvable problem occurred while calculating the upgrade

[Laurin Elis]

I tried upgrading to 20.04 LTS from 18.04.5 LTS already about a month ago, and it failed, but I thought that the problem occurred because I attempted it too early.
Well, now that I tried to perform the upgrade again, and it failed again, I think that there is a bigger problem.
At first, there was an explanation attached to the error message, that the problem was likely caused by "Unofficial software packages not provided by Ubuntu", so I disabled all ppas.
But I still got the error message "Could not calculate the upgrade", now without any likely causes listed. I disabled all repositories except the main one and the corresponding update and security repositories, but the problem still persists. According to the log file from /var/log/dist-upgrade/apt.log, I have 301 broken packages, but I simply don't understand how that's possible.
I've reenabled the restricted, universe and multiverse repositories, the number of broken packages stayed the same. do-release-upgrade and update-manager result in the same error. After running sudo apt update && sudo apt upgrade today, the number of broken packages according to the apt.log decreased to 220, but I still can't perform the upgrade.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.40
ProcVersionSignature: Ubuntu 5.4.0-52.57~18.04.1-generic 5.4.65
Uname: Linux 5.4.0-52-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Tue Nov 3 18:46:49 2020
InstallationDate: Installed on 2019-10-06 (394 days ago)
InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-11-03 (0 days ago)

[Laurin Elis (laurin01)]

Removing gnuradio fixed it.

[Brian Murray (brian-murray)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug 1898152, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.