Yes. Settings → Help Centre → Who can read it → Signed-in people only. Articles, topics, the front page and the search are then kept for people with an account on your site; a visitor is sent to sign in and brought back. Your theme's search, the REST API, the sitemap and link previews stop showing articles too. The support desk and the FAQ shortcode are not affected.
Still stuck? Ask the developers who wrote it. We aim to reply within one business day.
