Which Scripture? The Catholic, Orthodox, or Protestant one?
You're begging the question of whether Luther's canon of Scripture was determined infallibly.
Protestants tend to assume the truth of Luther's doctrine of Sola Scriptura. But that is what is in question in this thread.
If Luther didn't act infallibly in determining his canon of Scripture, then his doctrine of "the Bible alone" becomes incoherent, since there would exist no means by which anyone could determine what does and doesn't constitute sacred Scripture.
The scripture used by Protestants is not disputed by Roman Catholic as scripture, nor is it disputed by Eastern Orthodox.
Those books that were in dispute were not accepted as scripture, just as many early Church fathers did not accept them as scripture and just as the Roman Catholic Church did not accept them as scripture right up to the Protestant Reformation and beyond, until the Council Of Trent, and even then the theological issue was not resolved as to the canonicity of the Deuterocanonical books.
The Council Of Trent was itself a reaction to the Protestant Reformation.
So, what is your point? Are you still hunting in vain for a Protestant pope? I can assure you there is none, certainly not Martin Luther, nor John Calvin or Knox or Wesley. The head of the Church, the body of believers, is Jesus Christ.
I don’t see where Luther’s canon differed any from that of the canon of Augustine’s time. What he seemed to be rebelling against was the Council of Trent.
Scratch that, Trent occurred after Luther. Date confusion. Nonetheless, the Protestant canon aligns with the Hebrew bible.