There are no Knowledge Base and Category fields present on the sqanda_new_question page.
Steps to Reproduce
1 - Login an instance as any user
2 - Navigate to the portal page: /sp?id=sqanda_new_question
3 - Compared the fields displayed with the page: /$social_qa.do?sysparm_cancelable=true&sysparm_view=ask_question
This is expected behaviour in all current versions. Service Portal never intended to expose either of those fields and does not use them.
Related Problem: PRB824501