Here in the 1888 LDS edition, the modal shall was replaced by should. That edition never served as a copytext, so its reading was never copied into any subsequent LDS edition. As explained under Helaman 15:9, either shall or should can occur in lest- clauses, but should is more frequent, thus the tendency to change shall to should. For each case, the critical text will maintain the earliest reading, thus shall here in Mormon 8:17.
Summary: Maintain the modal shall in Mormon 8:17, the reading of both 𝓟 and the 1830 edition.