2.4 and BT aren’t the same thing, don’t trust ebay or aliecpress sellers over 8bitdo.
But on their boxes it’s explicitly saying BT. And in the linked video they show it working with BT with Nintendo Switch and Raspberry PI via BT dongle. So confusing :(
The n30 2.4g comes with the transmitter. And it’s a bog standard usb - not limited to the nes classic, so just grab one of those.
Are you sure? On the picture it looks different from the regular USB. And they explicitly mention only “NES Classic Edition”.