The 1892 RLDS edition omitted the expletive it here. Although an accident, the resulting reading is not impossible. Elsewhere in the text there are examples of “to X is given”, although in each of these cases there is an explicit subject following is given:
(In the last case, the that-clause appears to serve as the postponed subject for is given.) The major problem with the 1892 reading for Alma 29:5 is that there is no explicit subject following is given. Obviously, the original reading with the it will be maintained here in Alma 29:5.
Summary: Maintain the expletive it in Alma 29:5: “to him it is given according to his desires”.