But the verb in question is what “none” is doing, not “a number”, so that’s irrelevant. By analogy: “The singers are performing today, but one of them has a sore throat.” Introducing “one” doesn’t change the number of “singers”; it’s in a new clause. Bringing something irrelevant into it is what I called overthinking in the last comment.
“A number” is plural. You would not (I hope) say “A number of people has complained about my English.”
But the verb in question is what “none” is doing, not “a number”, so that’s irrelevant. By analogy: “The singers are performing today, but one of them has a sore throat.” Introducing “one” doesn’t change the number of “singers”; it’s in a new clause. Bringing something irrelevant into it is what I called overthinking in the last comment.
You are truly fortunate not to have that burden.