The official positions of at least several major denominations do indeed hold that the theology of Latter Day Saints is not Christian:
the Mormons are not to be considered as belonging to an "ecclesial community not in full communion with the Catholic Church" [...] if a Mormon wishes to become Catholic, the norms that regulate admission to the Church of non-Catholic Christians cannot be applied. [...] Mormons are to be considered non-baptized (Source; see also this)
The Lutheran Church—Missouri Synod, together with the vast majority of Christian denominations in the United States, does not regard the Mormon church as a Christian church.
Mormonism cannot be considered a Christian denomination. (Source)
I could not find a direct statement, however, a publication on baptism and Mormonism had this to say:
[Mormon] teaching about the nature of God is substantially different from that of orthodox, creedal Christianity. Because the Mormon understanding of the Word of God is not the same as the Christian understanding, it is correct to say that Christian Baptism has not taken place. (Source)
This question also asks about ELCA specifically. The top answer cites the same document.
The United Methodist Church recognizes the baptism of other Christian denominations [...] The Church of Jesus Christ of Latter Day Saints [...] is not what we consider Christian baptism. (Source)
The GOAoA's official stance is in line with that of the other churches already mentioned, but is expressed much less charitably. Accordingly, I decline to quote it. Read at your own risk. See also this, this and this, with the same disclaimer.
Mormonism is a new religious tradition distinct from the historic, apostolic tradition of the Church (source — not searchable, quote is from p2¶1)
Anglican / Episcopalian (Church of England)
I was unable to find any official statement, however I did find a document that had this to say:
The Anglican Church, the Episcopal Church [...] sees in the Book of Mormon a most interesting document, but not the Word of God. It is probably the first large-scale piece of American fiction. (Source; emphasis in original)
While the document does not seem (note that I only skimmed it) to explicitly call LDS non-Christian, it does assert that TBoM is in no way scriptural or spiritually useful and calls Mormonism a "new religion" which it contrasts with Christianity.
Additionally, a careful reading of this document, while not containing a direct statement, strongly implies that the A/E church does not consider LDS to be Christian. (The gist of the article — again, I only skimmed it — appears to be a complaint that the A/E church is more willing to engage with Jews and Muslims than with Mormons.)
While I have not found official statements, AFAICT the Church of England (see A/E, above) and Southern Baptist Church feel similarly. Pentecostals (at least the AoG) seem to share the GOAoA's stance, although I again could not locate any official statement. There may be other churches for which I tried and failed to find any explicit statement; this answer is substantially drawn from notes I recorded previously, and I did not record failures at the time.
Nevertheless, those churches that do have official statements on this question would seems to cover a fairly broad spectrum of other Christian churches. (Feel free to ask if you'd like me to specifically research any others. Beware, however, that it is difficult to find official statements from some of the more loosely organized churches.)
Please note these are not my personal opinions nor (as per the question) the opinions of random members of these churches, but are (as best I can determine) official opinions of various denominations generally accepted to be "Christian". In particular, I have tried to limit sources to official publications where possible.
Something else to keep in mind is that we are not generally discussing whether or not individuals are Christian, but whether a particular church considers the doctrine of LDS to be Christian. Just as Lutherans might consider the RCC to be heretical while still asserting that there are "true Christians" in the RCC in spite of this, most (non-LDS) churches would say that there may well be "true Christians" that are nominally Mormon/LDS in spite of the non-Christian (according to them) doctrine of the LDS. That is, there is a significant difference between the statements "the LDS is not a Christian church" and "(all) Mormons are not Christians".
do not consider Mormon baptisms validinstead of not Christian. Is it valid baptism that makes one Christian (If so who/what denotes validity)? related question and this one