Right now that data is not available directly from the ThingSpeak integration. We will consider it an enhancement request, thank you for the feedback. I would start by forwarding the packet that you get at TTN to a webhook reader. ( Ive used this site). Then find the key parts in the TTN packet, and write your payload formatter to translate the SNR information into the field data that you send to ThingSpeak. I'm not sure the payload formatter has access to the SNR parts of the packet though, I think it only applies to the payload section. The new TTN is pretty flexible though, so there may be a way. Good luck, please let us know if you get it worked out.