I am looking for pointers for libraries or methods that would be able to generate full text from the structured information returned by Wikidata - if possible in multiple languages.
To be clearer: from data like the one provided here (this is the JSON version) I would like to be able to generate text similar to the intro paragraph of the wikipedia page for the same item:
Orvieto Cathedral (Italian: Duomo di Orvieto; Cattedrale di Santa Maria Assunta) is a large 14th-century Roman Catholic cathedral dedicated to the Assumption of the Virgin Mary and situated in the town of Orvieto in Umbria, central Italy.
The reason is that the text is provided by Wikipedia for all those cases where a page exists, but I would like to have something also for the Wikidata items without a wikipedia page.
My problem #1 here is: I don't know what something like this is called, so I have no idea what to google for. Any pointers to start from are appreciated, including services or APIs.
This problem falls under the Data to text generation task. I do not know of any services that are currently offering solution. You can look at WEBNLG challenge which has the same objective and similar data. AFAIK mostly template based methods are used to automatically insert data from wikidata into wikipedia as text.