update fails from 18 to 20 but everything is ok

[Alberto]

I remove any possible ppa package
checked all dependencies
reinstalled lots of libs in the apt.log and main.log
no packages on hold

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.44
ProcVersionSignature: Ubuntu 4.15.0-142.146-generic 4.15.18
Uname: Linux 4.15.0-142-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.23
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: XFCE
Date: Thu Apr 29 19:37:04 2021
InstallationDate: Installed on 2017-12-24 (1222 days ago)
InstallationMedia: Xubuntu 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2021-04-29 (0 days ago)

[Brian Murray (brian-murray)]

Thanks for taking the time to report this upgrade failure. There is currently a new version of the release upgrader available in -proposed which may resolve the error you've encountered. Please run the following command to test the new version of the upgrader:

  do-release-upgrade -p

Please lets us know the results in this bug report. Thanks again and good luck!

[Launchpad Janitor (janitor)]

[Expired for ubuntu-release-upgrader (Ubuntu) because there has been no activity for 60 days.]