Is the Scannel Daguerreotype a confirmed photo of Joseph?
As far as we know, a Katherine Scannel (Mitchell?) donated this image to the RLDS church in 1969, along with a hymnal produced by Emma Hale Smith that bore the name "William Orr Scannel," claiming she inherited both from her ancestor, Emily L. Smith Scannel, who was supposedly a relative of Joseph's. Historian Ardis E. Parshall pieced together a possible provenance from that information.
Katherine Scannel was the daughter of Walter William Scannel (1887-1944).
Walter William Scannel was the son of Almon S. Scannel (1846-1918).
Almon S. Scannel was the son of William Orr Scannel (1801-1859) and Emily L. Smith (1809-1864).
So we do have limited evidence that the donor had ancestors that likely interacted with and were possibly members of the early LDS church (or at least appreciated their music) and that one of them may be a very distant relative of Joseph's. This does not establish the provenance of the photo, nor the identity of the man in it. For all we know, it could be William Orr Scannel himself, which would make more sense to me personally.
Neither the Community of Christ (the Reorganized Church of Jesus Christ of Latter Day Saints) nor the LDS Church have vouched for the identity of the man in the image, which was rediscovered in 1994 in the archives of the Community of Christ church in Independence, Missouri. In fact, the LDS church issued a statement in 2008 saying that the image could not be confirmed as genuine.
"A purported image of Joseph Smith is circulating widely on the Internet. Some persons have mistakenly claimed that this image belongs to The Church of Jesus Christ of Latter-day Saints and that Church officials have verified or are verifying its authenticity. These claims are not true.
This image, taken from a daguerreotype, belongs to the Community of Christ, formerly known as the RLDS church. On the basis of available evidence it is not possible to confirm that the image is, in fact, of Joseph Smith. The Church of Jesus Christ of Latter-day Saints does not have or own this photograph or any image of Joseph Smith other than several early artists' portrayals of him and some early photographs of those artists' portrayals. The Church does have the death mask of Joseph Smith."
The image is quite similar to the death mask, but some features shift significantly between the two.
On the left is the original image. The one on the right is reversed, since daguerreotype photography reversed the image laterally. The death mask is rotated to match the turned head in both versions, and the lighting is reversed to match, but the mask is not mirrored laterally since it is in the correct and original orientation. In either case, the eyes are too close together, the ala (wings of the nose) and apex (the tip) are too small, the chin is too small, and Joseph's unconscious smile, preserved even in death, is missing. Given the weak provenance of the photo, and these shifting features, it is unlikely that the man in this image is Joseph Smith.