17 files declare their use of FeedsPluginInterface in Feeds 8.3

CsvParserFeedFormTest.php in tests/src/Unit/Feeds/Parser/Form/CsvParserFeedFormTest.php

CsvParserFormTest.php in tests/src/Unit/Feeds/Parser/Form/CsvParserFormTest.php

DirectoryFetcherFormTest.php in tests/src/Unit/Feeds/Fetcher/Form/DirectoryFetcherFormTest.php

Feed.php in src/Entity/Feed.php

FeedForm.php in src/FeedForm.php

FeedInterface.php in src/FeedInterface.php

FeedTest.php in tests/src/Kernel/Entity/FeedTest.php

FeedTypeForm.php in src/FeedTypeForm.php

FetcherInterface.php in src/Plugin/Type/Fetcher/FetcherInterface.php

HttpFetcherFormTest.php in tests/src/Unit/Feeds/Fetcher/Form/HttpFetcherFormTest.php

ParserInterface.php in src/Plugin/Type/Parser/ParserInterface.php

PluginAwareInterface.php in src/Plugin/PluginAwareInterface.php

PluginFormFactory.php in src/Plugin/PluginFormFactory.php

ProcessorInterface.php in src/Plugin/Type/Processor/ProcessorInterface.php

SourceInterface.php in src/Plugin/Type/Source/SourceInterface.php

UploadFetcherFeedFormTest.php in tests/src/Unit/Feeds/Fetcher/Form/UploadFetcherFeedFormTest.php

UploadFetcherFormTest.php in tests/src/Unit/Feeds/Fetcher/Form/UploadFetcherFormTest.php