9 files declare their use of SqlContentEntityStorageSchema in Zircon Profile 8

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

Contains \Drupal\comment\CommentStorageSchema.

EntityTestStorageSchema.php in core/modules/system/tests/modules/entity_test/src/EntityTestStorageSchema.php

Contains \Drupal\entity_test\EntityTestStorageSchema.

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

Contains \Drupal\aggregator\FeedStorageSchema.

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

Contains \Drupal\file\FileStorageSchema.

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

Contains \Drupal\aggregator\ItemStorageSchema.

MenuLinkContentStorageSchema.php in core/modules/menu_link_content/src/MenuLinkContentStorageSchema.php

Contains \Drupal\menu_link_content\MenuLinkContentStorageSchema.

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

Contains \Drupal\node\NodeStorageSchema.

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

Contains \Drupal\taxonomy\TermStorageSchema.

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

Contains \Drupal\user\UserStorageSchema.