The United States has history of lurid anti catholic propaganda claiming that convents were endless lesbian orgies. Were there any actual nunneries that had lots of sexually active nuns? Did the the urban legends originate from these real incidents, or were they developed separately? Were accusations of homosexuality ever leveled against monasteries? Was there any truth to these accusations?
There were definitely some convents where all the accusations were true. I would recommend the recent, The Nuns of Sant'Ambrogio: The True Story of a Convent in Scandal by Hubert Wolf. It covers the story of a specific scandal that broke in 1858 where a charismatic nun, Maria Luisa, basically became a kind of a cult leader within the convent and engaged in sexual activity and encouraged other nuns to do the same basically as part of power politics. In this case the story was mostly hushed up. But some rumors did leak out and added to the common rumors.
However I think the vast majority of the stories were made up. The infamous 1836 Awful Disclosures by Maria Monk was denounced as a fraud after some Protestant clergy investigated her convent and discovered it was nothing like Monk described, and that Monk had spent time as a patient in a Catholic asylum. Humans being what they are though, the two pastors were denounced as Jesuits in disguise and the reporter, William Stone, that published their findings was prosecuted for taking bribes from Jesuits.