Lightning over LoRa is not going to work, lightning has far too much overhead and LoRa has really (really really really) low bandwidth (the noisefloor magic aint free). You could use another PHY, but then still you are just spinning a whole lot of wheels to get a simple transaction through. Future potential softforks might make it a bit better. 

Something like ecash makes more sense; even then you might want to consider if the overhead is worth it given you are dealing with such heavy technical (and legal/regelulatory) constrains working within the lower frequency ISM band options; combined with the inherrent inefficiencies of the mesh topology 

 #Reticulum