After googling for a TYPO3 extension, I became aware that the search result looked different:
There is information about how often this extension was downloaded, which category it belongs to, the last update of the extension and a link to the manual. For other extensions, there is also a link to the external repository, e.g. git.typo3.org, an information about the current version and more, it differs from extension to extension. This information is taken from the right side of the entry page of this extension in the TER (the TYPO3 Extension Repository):
The contents on the right side are not marked somehow as rich snippet / structured data, so it seems, Google (perhaps some kind of A.I. bot / machine learning crawler) recognized the TER and extracts this information of their own accord. Nice :)