Here the 1830 typesetter accidentally replaced which with that. Joseph Smith, following the 1830 edition, changed the original which in the printer’s manuscript to that as he was editing the text for the 1837 edition. There are a number of cases like this where Joseph, in his editing for the 1837 edition, made the printer’s manuscript agree with a change that the 1830 typesetter had earlier introduced into the text. For some other examples, see the emendations of partook to partake (in 1 Nephi 8:11) and murdereth to murdered (in Alma 1:18).
Nonetheless, there was no need here in Alma 27:20 to follow the 1830 edition. Statistically, the phrase “all the things which” is more frequent in the Book of Mormon text than “all the things that” (10 to 3):
Grammatically there is nothing wrong with using which in a restrictive sense, despite the prescriptive claim to the contrary. See the first section under that in Merriam Webster’s Dictionary of English Usage.
Summary: Restore the original and fully grammatical “all the things which” in Alma 27:20.