A loRa network consists of a gateway (in the middle, talking to a backend via a backhaul (eg internet)) and one or more nodes around it. Think of it as a star-shaped pattern.
One node does not known of the existence of the other, they cannot 'speak' to each other. They do share the same frequencies (to be precise 8 of them) so they could be talking at the same time on the same frequency. But you'd better see this as both of them shouting without listening
I seriously doubt if it's possible to let one RN2483 think it's a gateway as the chip has the LoRa stack built into itself. But maybe someone else, with more knowledge knows a way to get this done, legally. I know of the RFM modules (another chip) to be able to operate as a single channel gateway.