If you download the zip file and extract it.
Go the the folder wow-ui-source-10.2.7\Interface\AddOns\Blizzard_Settings_Shared
and open the Blizzard_Deprecated.lua file.
You will see the function containing the new code that was used through Dragonflight to replace InterfaceOptions_AddCategory.
You can adapt that code to your addon to replace the function.