What is the ruling regarding a mosque imam who, after rising from bowing (rukuʿ) in the second rakʿah of the Fajr prayer, remains silent to allow the Shafi'i congregants to perform qunut, knowing that the imam does not consider qunut valid and the congregants reject that [stance]?

The Companions, the Tabi'un, and the scholars differed concerning the Qunut in the Fajr prayer. It is permissible for the Imam to perform the Qunut or not to perform it. If the Imam does not perform it, then it is permissible for a worshipper who believes in the Qunut to perform it if he knows he will catch up with the Imam in prostration. It is not required for the Imam who does not believe in the Qunut to stand silently to allow the worshipper an opportunity; rather, he may either perform the Qunut (which is permissible) or occupy himself with the reported supplication after rising from bowing.