Turn off the site setting discourse narrative bot enabled.
Or, even better, keep it enabled but instead change the setting discourse narrative bot welcome post type to Send all new users a welcome message with a quick start guide. Instead of the tutorial, Discobot will send a simple, non-interactive welcome message that will automatically close to prevent user replies.
Like all Discourse texts, you can customize the welcome message by navigating to Admin > Customize > Site Texts at the following path:
/admin/customize/site_texts?q=system_messages.welcome_user.text_body_template.
Within this string, you’ll find the variable %{new_user_tips}, which corresponds to another string: system_messages.usage_tips.text_body_template.
By modifying the text of one or both strings and setting the discourse narrative bot welcome post type to Send all new users a welcome message with a quick start guide, you should be able to create the customized message without triggering the interactive tutorial.