Yes, definitely are L for left, R for right and G for GND.
In order to improve contact, we have started the email list. I have found that forums are difficult to interact with - because they don't allow email reply. We also tried GitHub issues for support, however they are too disjoint and it is difficult for many people to have discussions. Also on GitHub people always want to close issues, we prefer discussions. So for that reason we have reverted to a community group on good old mailman !
Discuss hearing, acoustics, audio injector products, - https://lists.audioinjector.net/mailman/listinfo/people
Sound card for the Raspberry Pi with inbuilt microphone : www.audioinjector.net
Audio Inector Octo multitrack GPIO sound card