I have an OSSC 1.6, with the 0.80a firmware. Sound over RGB scart and AV1 works. Today, I tried to use component input today from my Wii (using an official nintendo branded component cable), with the audio inputs plugged into a 2.5mm stereo jack adapter, and there is no sound. I toggled the switch on it to select AV2 input, instead of it being on AV1 output, and still no joy. TX is set up to use HDMI. I have tried a few HDMI cables, same result. These same HDMI cables transmit sound just fine from the SCART input.
If I plug the audio out from the component cable into a mobile speaker I have, using the same RCA to 2.5mm jack adapter I am using with the OSSC, sound plays just fine.