Latter-day Saints don’t claim the Bible was corrupted beyond recovery, only that plain and precious things were lost before the earliest manuscripts. Preservation of what survives doesn’t show nothing was removed.

This is the precise LDS position, and it is the one to engage. The reply is that the loss would have to predate every manuscript, version, and patristic quotation, and that the specifically LDS doctrines allegedly removed are absent from all early Christian literature, including sources hostile to the mainstream, which is what one would expect if they were never there. The Joseph Smith Translation’s changes have no manuscript support of any kind. Corrupted compared to what earlier standard is answered by the Book of Mormon and the JST, which are nineteenth-century texts whose claim to reflect the original is what needs demonstrating; using them as the standard assumes the conclusion.