Here the 1920 LDS edition grammatically emended whosoever to whomsoever, in accord with the prescriptive grammatical rule that whosoever takes the subject or object form according to the role it plays within the who(m)soever clause itself, as in “I gave the book to whosoever wanted it” versus “I gave the book to whomsoever I liked”. Here in Mosiah 26:22, the subject for the nominal clause is ye; therefore who(m)soever is the direct object within that clause and, according to prescriptive grammar, should be whomsoever. As in the case of who versus whom, the critical text will follow the earliest reading, not necessarily what is prescribed. For further discussion of subject versus object forms of pronouns, see under pronouns as well as under which in volume 3.
Summary: Maintain in Mosiah 26:22 the original whosoever in the nominal relative clause “whosoever ye receive” even though whosoever is acting as the direct object within the nominal clause itself.