RAK612 to ProPTT2Server Connectivity Example

Is it possible to connect a 4 button RAK612 to a ProPPT2Server? The example code I see it connecting to The Things Network TTN. I sort of envision the RAK612 device connecting to a RAK7258 device which provides connectivity to a PTTServer. At this point then envision the PTTServer forwarding the ‘button push’ messages to other PTTClient applications. Is this possible or am I off in the weeds? If so, can you provide some links as to where to read more to become more comfortable with the feasibility?
Thank you very much.