I have to say that it is quite a shame that Canonical does not provide a proper solution for this problem, as it has quite a big impact if you cannot update packages with security fixes anymore.
Anyway, I managed to solve the problem. From an earlier repo installation, I had a key file with the troubling filename "isv:ownCloud:desktop.asc" at "/etc/apt/trusted.gpg.d". After removing that file ("sudo rm /etc/apt/trusted.gpg.d/isv:ownCloud:desktop.asc") I was able to import new keys again. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to apt in Ubuntu. https://bugs.launchpad.net/bugs/1912526 Title: cannot import new keys if another malformed key exists Status in apt package in Ubuntu: New Bug description: "apt-key add" fails to import keys if there exists another key with a malformed file name. Such malformed key names used to be provided by the openSUSE Build Service (https://github.com/openSUSE/software-o-o/issues/842). After importing such malformed key, future key imports will fail with something like: $ sudo apt-key add linux_signing_key.pub gpg: invalid key resource URL '/tmp/apt-key-gpghome.f8IaqZ48Ze/isv:ownCloud:desktop.asc.gpg' gpg: keyblock resource '(null)': General error even though no such file "isv:ownCloud:desktop.asc.gpg" exists anywhere on the filesystem. This affects deb packages that import public repo keys during installation, such as Google Chrome or Vivaldi, and results in minor issues such as breaking GUI tools and CLI warnings, and the major issue that the installed repo cannot be used anymore to update the software (Google Chrome, Vivaldi). apt-key should be robust to such issues and continue importing keys. As in the example above, apt-key should import "linux_signing_key.pub" no matter if another unrelated key is malformed etc. ProblemType: Bug DistroRelease: Ubuntu 20.04 Package: apt 2.0.2ubuntu0.2 ProcVersionSignature: Ubuntu 5.8.0-38.43~20.04.1-generic 5.8.18 Uname: Linux 5.8.0-38-generic x86_64 NonfreeKernelModules: openafs nvidia_uvm nvidia_drm nvidia_modeset nvidia ApportVersion: 2.20.11-0ubuntu27.14 Architecture: amd64 CasperMD5CheckResult: skip CurrentDesktop: ubuntu:GNOME Date: Wed Jan 20 19:24:34 2021 InstallationDate: Installed on 2020-04-24 (271 days ago) InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423) SourcePackage: apt UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/apt/+bug/1912526/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp