On a fresh TYPO3 13.4 Version the following error appears:
(1/1) #1404068038 InvalidArgumentException
No extension key could be determined when calling addPlugin()! This method is meant to be called from Configuration/TCA/Overrides files. The extension key needs to be specified as third parameter. Calling it from any other place e.g. ext_localconf.php does not work and is not supported.