It looks like this file was not written during the update: https://github.com/piwik/piwik/blob/2.16.5/plugins/CorePluginsAdmin/config/config.php

To solve this create a file plugins/CorePluginsAdmin/config/config.php using content of https://raw.githubusercontent.com/piwik/piwik/2.16.5/plugins/CorePluginsAdmin/config/config.php

The module is there, with the same content.

Does it still not work? I will reopen the issue.

What's your PHP version and operating system?

I'd recommend to execute the update again, but this time manually see http://piwik.org/docs/update/#the-manual-three-step-update . Important: backup your config/config.ini.php before doing so

I'm using the docker image from https://github.com/piwik/docker-piwik.

The update consisted of changing the image version in my Dockerfile and recreating the container, the database is in a separate data volume.
On first visit after the update there was a message about existing tables and I opted to use the existing ones. These steps worked without issues for the last couple of updates.

I have called console core:update, it says everything is already up to date.

I'll try reproducing with a new container and database, is marketplacePiwikVersion supposed to be present somewhere as a db entry, or only in the php code?

It is supposed to be only in the PHP code

It turns out CustomDimensions was listed in config without really being activated, after sorting out the config and activating the plugin, the issue disappeared.

Awesome, glad to hear this