One theory is that the server returned 304 (not modfied) for all requests. This might in theory result in a empty /var/lib/apt/lists and would explain the behavior that no upgrades (other than security.ubuntu.com) could be found.
One theory is that the server returned 304 (not modfied) for all requests. This might in theory result in a empty /var/lib/apt/lists and would explain the behavior that no upgrades (other than security. ubuntu. com) could be found.