Is the widespread hadith: "At the end of time there will come men, who are not truly men, they imitate women; if you see them, then know that the Hour has drawn near" authentic, and is its attribution to the Prophet, may Allah bless him and grant him peace, sound?

Many hadiths have been narrated condemning men's imitation of women and women's imitation of men, and cursing those who do so. However, the hadith with the wording mentioned in the question has no origin in the books of Sunnah. Abu Nu'aym did narrate a hadith in "Hilyat al-Awliya'" mentioning 72 signs of the approaching Hour, among them "men imitating women and women imitating men." However, this hadith is weak due to Suwayd ibn Sa'id al-Hadathani and Faraj ibn Fadalah, and due to an interruption in its chain of transmission because Abdullah ibn Ubayd al-Laythi did not hear from Hudhayfah. Despite the weakness of this hadith, some of its sections have authentic corroborating evidence. As for men imitating women, it is an objectionable and forbidden act, but there is no authentic evidence in the Prophetic Sunnah that it is one of the signs of the Hour.