Oliver Cowdery initially wrote “the Lord receiveth them up to himself ”, then virtually immediately corrected the to to unto by inserting inline un before the to (and without any change in the level of ink flow). Either preposition is theoretically possible here. Elsewhere the text has examples of either preposition after the adverb up, as in these two pairs of examples:
Thus the critical text will maintain the corrected reading in 𝓟 for Alma 14:11 (“the Lord receiveth them up unto himself”). The original manuscript probably had unto rather than to since there would have been no motivation for Oliver to have otherwise emended to to unto.
Summary: Maintain in Alma 14:11 the preposition unto in “the Lord receiveth them up unto himself ”, the corrected reading in 𝓟.