Is Hafs the narrator, the nephew of Anas, unknown, as Ibn Hazm said, or is he trustworthy and truthful, as Al-Haythami and Ibn Hajar said? And did anyone else declare him unknown besides Ibn Hazm?

Ibn Hazm denied the existence of Hafs ibn Akhi Anas, even though Hafs is the son of Anas's sister (i.e., his maternal nephew). Al-Mizzi mentioned various accounts regarding Hafs's lineage, and he narrated from his maternal uncle Anas. Al-Daraqutni, Abu Hatim, and Al-Dhahabi all authenticated him. No one followed Ibn Hazm in declaring Hafs unknown.