Hi,
after performing the update to Tuleap 11.8.99.50, my Administration > Plugins page showed the following notification:

After following the instructions, the notification showed:

When running /usr/lib/forgeupgrade/bin/forgeupgrade --config=/etc/tuleap/forgeupgrade/config.ini update the output showed:
ERROR - An error occured while adding the column notification_occurence to the table plugin_docman_approval
Running the same command without the plugins/docman entry on the config.ini file, the output is:
INFO - System up-to-date