The only evidence at all that any canon of scripture was discussed at the Council of Nicea is St. Jerome’s odd claim that the Book of Judith *was* included in the canon at that Council.
The Protestant fascination with St. Jerome’s canon amazes me. If the Protestant position is true, that St. Jerome intended to insist that the deuterocanonical books were not part of Holy Scripture and that he only later insisted they were because he “caved to Popish corruption,” all that proves is that yes, the Catholic Church did have a canon at that time, and that she was so adamant on it that St. Jerome could not withstand her on the matter.
We know is that Jerome noted that the Jews among whom he studied did not consider the deuterocanonicals scripture and that he couldn’t translate what he didn’t have. We know he was scandalized by the profound differences between the Jewish and Greek versions of the bible, and that he falsely believed that the Greek versions he had were merely later, error-filled translations. (I say “falsely,” because we now know the Greek versions also predated Jesus and the citations made by Jesus match far, far more closely the Greek versions.) We know that reasonable-seeming people understood his commentary to mean he was denigrating the deuterocanonicals, but that he responded to them angrily as “fools and slanderers.”
The extended version of the prayer of the three youths in the furnace (Daniel) is one of the weekly canticles, despite being in dueterocanonical part of Daniel; it has been since antiquity central to Eastern liturgies, including the Syro-Malabar rite, which was independent from any Western influence between the 3rd and 15th centuries.
I apologise, you are correct with regard to Jerome.