ENT, Ortho, Ophthamology, Neurosurgery, and Urology are direct matches only.
Plastic Surgery, Thoracic Surgery, and Cardiothoracic can be direct matches (known as integrated programs) or you can get them through General Surgery by applying to these areas as fellowships. Benefits of these are saved years, earlier exposures to the fields, and of course a guarantee without the need of possibly taking more research years to be competitive. The above is not an exhaustive list of General Surgery fellowships and there’s tons of others in things like colorectal surgery, minimally invasive surgery, etc.
I’ve anecdotally heard of case where a surgery resident informally got offered a spot in Neurosurgery when someone dropped it, but he didn’t take it. I don’t know if it was true, but be aware that there may be some informal stuff going on within the department. I would still imagine these situations being rare and would not go for a Gen Surg spot (especially prelim) with the hopes of getting into a competitive subspecialty that’s not accessible via Gen Surg fellowship.