I'm not sure what specific aspects of ONFi you are looking to use. The FMC (External Bus) on the H7 is rather agnostic to the hardware interface specifics, and has a finite set of pins to implement memory banks/selects. If you need additional signals perhaps look at how you can use address bus bits to drive them, and then use offsets within the decode window to actuate those signals high/low.
Any query methods on the array/geometry would need to be implemented in user's driver code.
