/etc/xdg/kaddressbook.categories is in kaddressbook 4:17.12.3-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | org.kde.pim.kaddressbook kaddressbook (kaddressbook)
org.kde.pim.kaddressbook_plugin kaddressbook (kaddressbook kontact plugins)
|