If conflicting claims as to the domicile of a decedent are made in a formal testacy or appointment proceeding commenced in Nebraska and also in a testacy or appointment proceeding after notice pending at the same time in another state, with an applicable provision of law similar in reciprocal effect to this provision, the court in Nebraska is required to stay, dismiss, or permit suitable amendment in the proceeding here unless it is here determined that the local proceeding was commenced before the proceeding elsewhere, and the determination of domicile in the proceeding first commenced is determinative in the proceeding in Nebraska.