I encountered the same problem trying to update a package (exim4 as it happens) whose configuration file I had previous modified. muon-updater just hung "Waiting for configuration file". muon-updater didn't provide a way to exit it cleanly, so I ended up killing it externally. Then had to kill two qaptworker2 processes so that the lock on the package database was released. Then
I encountered the same problem trying to update a package (exim4 as it happens) whose configuration file I had previous modified. muon-updater just hung "Waiting for configuration file". muon-updater didn't provide a way to exit it cleanly, so I ended up killing it externally. Then had to kill two qaptworker2 processes so that the lock on the package database was released. Then
$ sudo dpkg --configure -a
completed the update.