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 Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1912526 Title: cannot import new keys if another malformed key exists To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/apt/+bug/1912526/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs