22 files declare their use of PluginException in Drupal 9

BlockPluginCollection.php in core/modules/block/src/BlockPluginCollection.php

BlockStorageUnitTest.php in core/modules/block/tests/src/Kernel/BlockStorageUnitTest.php

ContextualLinkManager.php in core/lib/Drupal/Core/Menu/ContextualLinkManager.php

DefaultFactory.php in core/lib/Drupal/Component/Plugin/Factory/DefaultFactory.php

DefaultFactoryTest.php in core/tests/Drupal/Tests/Component/Plugin/DefaultFactoryTest.php

DefaultPluginManagerTest.php in core/tests/Drupal/Tests/Core/Plugin/DefaultPluginManagerTest.php

DisplayPluginCollection.php in core/modules/views/src/DisplayPluginCollection.php

ExecutablePluginBase.php in core/lib/Drupal/Core/Executable/ExecutablePluginBase.php

InaccessibleMenuLink.php in core/lib/Drupal/Core/Menu/InaccessibleMenuLink.php

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

LocalTaskManager.php in core/lib/Drupal/Core/Menu/LocalTaskManager.php

MenuLinkBase.php in core/lib/Drupal/Core/Menu/MenuLinkBase.php

MenuLinkContent.php in core/modules/menu_link_content/src/Plugin/Menu/MenuLinkContent.php

MenuLinkManager.php in core/lib/Drupal/Core/Menu/MenuLinkManager.php

MenuLinkPluginConverter.php in core/lib/Drupal/Core/ParamConverter/MenuLinkPluginConverter.php

MenuTreeStorage.php in core/lib/Drupal/Core/Menu/MenuTreeStorage.php

MenuTreeStorageTest.php in core/tests/Drupal/KernelTests/Core/Menu/MenuTreeStorageTest.php

MigrateLookup.php in core/modules/migrate/src/MigrateLookup.php

MigrateLookupTest.php in core/modules/migrate/tests/src/Unit/MigrateLookupTest.php

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

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

TypedDataManager.php in core/lib/Drupal/Core/TypedData/TypedDataManager.php