When trying to install updates via Software Updater I get the following message:
"The package system is broken Check if you are using third party repositories. If so disable them, since they are a common source of problems.
Furthermore run the following command in a Terminal: apt-get install -f"
Also, Software Updater crashes.
I would like to do as the above message says and disable third pary repositories, but in Software & Updates there is no option that (explicitly) mentions "third party repositories".
In the top right corner of my screen is a do-not-enter sign - clicking it shows another message saying an error occurred ("Error Broken count >0").
Maybe it is related to Chromium Web Browser, because in the crash report it says
Title: update-manager crashed with chromium-browser-l10n in_show_transaction(): Depends: chromium-browser (>= 59.0.3071.109-0ubuntu0.16.04.1291) but 58.0.3029.110-0ubuntu0.16.04.1281 is installed
I thought deselecting Chromium Web Browser in Software Updater might let me install other updates but I cannot deselect it. I can deselect everything else.
I tried uninstalling the browser but this did not help.
As brndn2k suggested, running
sudo apt-get install -ffixed it.