You can try the following (but I don't know whether it will work) - open .kde/share/config/activitymanager-pluginsrc and add the following to the [Global] section:
disabledPlugins=activitymanager_plugin_nepomuk
So the file would look something like this (and restart KAMD)
[Global] disabledPlugins=activitymanager_plugin_nepomuk
You can try the following (but I don't know whether it will work) - open .kde/share/ config/ activitymanager -pluginsrc and add the following to the [Global] section:
disabledPlugins =activitymanage r_plugin_ nepomuk
So the file would look something like this (and restart KAMD) =activitymanage r_plugin_ nepomuk
[Global] disabledPlugins