During the reign of Vladimir the Great, several envoys were sent from his court to study the religions of various neighboring nations with the goal finding a good one to convert his nation too.
Ukrainian sources say one of the religions his envoys studied and subsequently talked about with him was the Jewish faith. Eventually he said no to this prospect, and converted to christianity.
But what if, instead of choosing the Orthodox church, he went with the Jewish faith?
What would be the butterflies?
I seriously doubt that story ever happened in real life. Vladimir's own grandmother, Saint Olga, converted to the Greek Christianity of Constantinople many years earlier. They were the most common sort of Christians in Rus territory. And it was the Byzantine Empire which had significant geo-political influence in the region for some time. Plus, he was marrying the Byzantine princess, Anna Porphyrogenita, sister of Basil II. I'm not sure that they would have ever given away one of the princesses to someone who did not convert before hand.
With all that in mind, I don't see why Vladimir would have needed to choose any alternate religions. If his conversion was spurred by the prospects of an imperial marriage, then I doubt he would have converted at all. He probably thought that his baptism was a mere formality, a means to an end, and would have continued worshipping Perun, Veles and Svarog anyway. His new wife's influence with him, preaching Christ in their bedchamber, would have informed his later actions.
There were political benefits, for kings and chieftains, to convert to Christianity. I truth, the Khazars were very pluralistic in religious terms, and the adopted Judaism of the ruling family was not shared by everyone. Nor was it enforced.
If Vladimir decided on Islam, then it would have been moved by the prospect of a dynastic marriage with a princess of the Abbasid Caliphate. But that's too far away, and Constantinople was closer. And there was the high number of Greek Christians from the more affluent Crimea living in Kievan territories. If the Rus were ever going to adopt a new religion, then by this stage it was going to be Christianity.