Here in the 1906 LDS edition, the present-tense hath was replaced by the past-tense had, apparently because of the two correct occurrences of had in the subsequent text. The 1906 edition never served as a copytext; thus this error was never transmitted into any subsequent LDS edition. Elsewhere, when the narrator refers to something as having been revealed unto him, we get the present-tense form of the perfect auxiliary:
Interestingly, in the first case (in Alma 11:31) the original hath was replaced by had in the 1874 RLDS edition, just like here in Ether 8:20 for the 1906 LDS edition. The critical text will, to be sure, follow the present-tense form of the perfect auxiliary in all these cases.
Summary: Maintain in Ether 8:20 the present-tense hath in “it hath been made known unto me”, the earliest reading.