There was an input/output error when installing the package, possibly caused by a disk problem. Could you please try to re-install and let us know whether this works (copy/paste the output of the following command here):
sudo apt reinstall thunderbird ** Changed in: thunderbird (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1882446 Title: package thunderbird 1:68.7.0+build1-0ubuntu2 failed to install/upgrade: unable to make backup link of './usr/lib/thunderbird/libxul.so' before installing new version: Input/output error To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/thunderbird/+bug/1882446/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs