8 files declare their use of ContentEntityStorageInterface in Zircon Profile 8

CommentStorageInterface.php in core/modules/comment/src/CommentStorageInterface.php

Contains \Drupal\comment\CommentStorageInterface.

FeedStorageInterface.php in core/modules/aggregator/src/FeedStorageInterface.php

Contains \Drupal\aggregator\FeedStorageInterface.

FileStorageInterface.php in core/modules/file/src/FileStorageInterface.php

Contains \Drupal\file\FileStorageInterface.

ItemStorageInterface.php in core/modules/aggregator/src/ItemStorageInterface.php

Contains \Drupal\aggregator\ItemStorageInterface.

KeyValueContentEntityStorage.php in core/lib/Drupal/Core/Entity/KeyValueStore/KeyValueContentEntityStorage.php

Contains \Drupal\Core\Entity\KeyValueStore\KeyValueContentEntityStorage.

NodeStorageInterface.php in core/modules/node/src/NodeStorageInterface.php

Contains \Drupal\node\NodeStorageInterface.

TermStorageInterface.php in core/modules/taxonomy/src/TermStorageInterface.php

Contains \Drupal\taxonomy\TermStorageInterface.

UserStorageInterface.php in core/modules/user/src/UserStorageInterface.php

Contains \Drupal\user\UserStorageInterface.