I've been told by a few separate people that Sefer Devarim (as evidenced by historians' accounts and the stylistic differences between it and the other 4 books of Torah) was in fact written at a later time than the rest of the Torah. I have heard many Rabbis say this is untrue but without backing it with any evidence while the people who pose this contention quote various historians who mention parades in the Jewish community after Sefer Devarim was "found."
Does anyone have any information on this topic or references to shed light on the matter?
Edit: This is unlike the other article and question that people think this is a duplicate of. That is going down a theological and philosophical wormhole I have no interest it. I am merely asking about Devarim and the contention that it is not part of the original Torah. I dont see how the other question answers mine.