Ketchup?
Certainly, if you don’t have any cheese curds and warm brown gravy to pour over them.
I used to dress them with salt, vinegar, and ketchup when I was young.
The only time I have been exposed to fries with mayonnaise, was at stop at a MacDonalds on I-95, in the early 90’s, Georgia or S.C, I believe, and all they offered was mayo, no ketchup.
She said...”What? Ketchup? For your fries???”
LMAO!