John Gilbert, the 1830 typesetter, initially interpreted Oliver Cowdery’s fathers in 𝓟 as the possessive singular father’s: using pencil in the print shop, Gilbert placed in 𝓟 an apostrophe before the final s. He soon changed his mind, crossed out that apostrophe, and wrote one after the final s. Thus he ended up interpreting “their fathers inheritance” as “their fathers’ inheritance”, which is obviously correct given that the Lamanites’ fathers were Laman, Lemuel, and the sons of Ishmael.
We have a similar situation regarding the apostrophe in Alma 21:1. There the phrase “their fathers’ nativity” was originally misinterpreted by the 1852 typesetter as “their father’s nativity”. As explained under Alma 21:1, the text there is referring to the Lamanites and their fathers: namely, Laman, Lemuel, and the sons of Ishmael.
Summary: Accept in Alma 22:28 the 1830 typesetter’s interpretation of fathers in 𝓟 as the possessive plural fathers’ (thus “in the place of their fathers’ inheritance”).