As discussed under 1 Nephi 14:28, the critical text will restore the original not in this sentence. The LDS text has removed the multiple negation, but the RLDS text has not (which shows that there is only a weak sense of multiple negation in this construction involving but ). For a complete discussion regarding negation in the Book of Mormon text, see under negation in volume 3.
Summary: Restore the original not in Alma 58:5, “this did not profit us but little”.