Hugh Nibley discusses the authorship of Isaiah.
Hugh Nibley, The Collected Works of Hugh Nibley, Vol. 7: Since Cumorah (Salt Lake City, Deseret Book Co., 1988) Kindle Locations 3626-3632
We have spent too long on an issue that will probably remain unsettled in our generation, but the net result of our little filibuster is not without justification. The indications are that a thorough study of the rapidly changing Isaiah problem may well leave the Book of Mormon in a very strong position indeed. The dating of either the whole or any part of the Deutero-Isaiah must remain uncertain as long as there is no agreement among the experts as to the relationship of the parts to each other or as to the nature, authorship, or background of the whole. And as long as no one has produced or can produce irrefutable proof that any single Isaiah verse quoted in the Book of Mormon could not have been written before 600 B.C., or indeed has not been defended by reputable scholars as the product of a much earlier time, the chronological question remains wide open.