@burgeh It is definitely possible, if you use raw LoRa mode. The simple expamples from the docs would serve for LoPy. I do not know how you want to drive the RN2903.
Dear Emmanuel,
As i mentioned in my reply about a month ago, i could get it working when shifting the frequency a bit. Not sure what is causing it, but then communication could be established as well for uplink, downlink message as join requests.