From View profile of other users as contacts? & Expose system address book by schiessle · Pull Request #23199 · nextcloud/server · GitHub, it looks like a feature was added to have “Expose system address book” option in the Admin > Groupware settings.
However, it appears the “Expose system address book” is not present. Has it been moved or removed?
Under the Admin > Groupware > Contacts, I see
