I think you’ll have to use the rails console for that one.
# ssh into server
cd /var/discourse
./launcher enter app
rails c
Category.pluck(:name, :topic_id)
You will get back a list of category names and their associated topic_id.
If the one you’re looking for is “nil”, you could try that in the rails console
Topic.unscoped.where("title ILIKE 'About %'").pluck(:title, :id)