Is it permissible for someone who has missed a prayer to join a latecomer (masbuq) in congregational prayer who has completed his prayer? And is the hadith, "There is no imamate for a follower (ma'mum)," authentic?

Scholars have differed on the ruling concerning a latecomer (masbuq) leading the prayer, with two opinions. The preponderant view is the validity of his imamate and the permissibility of following him. As for the mentioned hadith, it was not authentically reported from the Prophet, peace and blessings be upon him.