I just looked it up on Wikipedia. The historians in the tenth century, etc., stated that the Khazars converted to Judaism. Go take it up with them.
As for as DNA, at the end of the article, after much discussion, it merely states that there exists no modern control group to compare DNA.
As for Koestler, I have read his novels and non-fiction works and the man was brilliant and a Jew himself.
You skipped 1/2 dozen articles at that link showing the myth is garbage and the DNA proves conclusively its a myth. Wikipedia is run by Leftists.
PS - Theres no dispute that the “The historians in the tenth century, etc., stated that the Khazars converted to Judaism.
the dispute is over whether it was just the rulers / ruling class and/or the populace, AND the asinine claim that all the Jews who had migrated into Europe were wiped out exterminated/assimilated before then, AND thus the converted Khazara are the source of all Ashkenazi Jews.
And THAT is ALL BULLSHIT.