Error: Private files directory not fully protected I received the following error in my Drupal 8 status report:

PRIVATE FILES DIRECTORY Not fully protected See
https://www.drupal.org/SA-CORE-2013-003 for information about the
recommended .htaccess file which should be added to the private://
directory to help protect against arbitrary code execution.

The obsolete link provided shows no guidance for Drupal 8 or 9, only 7 and prior. I already have what I believe is a strict .htaccess file I'd found elsewhere in Drupal's documentation. How can I fix this error in Drupal 8?
Submit the admin form @/admin/config/media/file-system will also create this .htaccess file if your folders are setup correct.