7 files declare their use of EntityConfigBase in Zircon Profile 8

EntityBlock.php in core/modules/block/src/Plugin/migrate/destination/EntityBlock.php

Contains \Drupal\block\Plugin\migrate\destination\EntityBlock.

EntityCommentType.php in core/modules/comment/src/Plugin/migrate/destination/EntityCommentType.php

Contains \Drupal\comment\Plugin\migrate\destination\EntityCommentType.

EntityDateFormat.php in core/modules/system/src/Plugin/migrate/destination/EntityDateFormat.php

Contains \Drupal\system\Plugin\migrate\destination\EntityDateFormat.

EntityImageStyle.php in core/modules/image/src/Plugin/migrate/destination/EntityImageStyle.php

Contains \Drupal\image\Plugin\migrate\destination\EntityImageStyle.

EntityNodeType.php in core/modules/node/src/Plugin/migrate/destination/EntityNodeType.php

Contains \Drupal\node\Plugin\migrate\destination\EntityNodeType.

EntitySearchPage.php in core/modules/search/src/Plugin/migrate/destination/EntitySearchPage.php

Contains \Drupal\search\Plugin\migrate\destination\EntitySearchPage.

EntityShortcutSet.php in core/modules/shortcut/src/Plugin/migrate/destination/EntityShortcutSet.php

Contains \Drupal\shortcut\Plugin\migrate\destination\EntityShortcutSet.