12 files declare their use of ConfigEntityUpdater in Drupal 8

action.post_update.php in core/modules/action/action.post_update.php

Post update functions for Action module.

block_content.post_update.php in core/modules/block_content/block_content.post_update.php

Post update functions for Custom Block.

ConfigEntityUpdaterTest.php in core/tests/Drupal/KernelTests/Core/Config/Entity/ConfigEntityUpdaterTest.php

content_moderation.post_update.php in core/modules/content_moderation/content_moderation.post_update.php

Post update functions for the Content Moderation module.

image.post_update.php in core/modules/image/image.post_update.php

Post-update functions for Image.

layout_builder.post_update.php in core/modules/layout_builder/layout_builder.post_update.php

Post update functions for Layout Builder.

layout_discovery.post_update.php in core/modules/layout_discovery/layout_discovery.post_update.php

Post update functions for layout discovery.

search.post_update.php in core/modules/search/search.post_update.php

Post update functions for Search module.

system.post_update.php in core/modules/system/system.post_update.php

Post update functions for System.

taxonomy.post_update.php in core/modules/taxonomy/taxonomy.post_update.php

Post update functions for Taxonomy.

text.post_update.php in core/modules/text/text.post_update.php

Contains post update hooks for the text module.

views.post_update.php in core/modules/views/views.post_update.php

Post update functions for Views.