6 files declare their use of LayoutEntityDisplayInterface in Drupal 9

DefaultsEntityForm.php in core/modules/layout_builder/src/Form/DefaultsEntityForm.php

DefaultsSectionStorageTest.php in core/modules/layout_builder/tests/src/Unit/DefaultsSectionStorageTest.php

LayoutBuilderEntityViewDisplayForm.php in core/modules/layout_builder/src/Form/LayoutBuilderEntityViewDisplayForm.php

LayoutEntityDisplayNormalizer.php in core/modules/layout_builder/src/Normalizer/LayoutEntityDisplayNormalizer.php

LayoutEntityHelperTrait.php in core/modules/layout_builder/src/LayoutEntityHelperTrait.php

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

Post update functions for Layout Builder.