This is release 1.17 of the Search API module, containing several bug fixes and new features.
Caution: If you are updating from version 8.x-1.15 or earlier, please note that, as this release changes a service definition, clearing the cache a second time after deploying (via drush cr or running update.php again) might be necessary. (See #3126367: TypeError: Argument 2 passed to SearchApiConverter::__construct() must implement EntityRepositoryInterface.)
drush cr
update.php
This is the first Search API release fully compatible with Drupal 9.