It is pretty cool! Saved my bacon for a really niche use case. Each 3.5mm out is 2 channels: Front L/R; Rear L/R; Rear Surround L/R; and Center/Sub. So one 3.5mm per 2 channels --> 1 RCA per channel.
The niche use I might have for this device is for driving an old (pre-DD+) AVR from a Roku via optical. I’m using an old 4640 Roku Ultra, which is the last Roku model that does transcoding of DD+ to DD optical. The 4640 is working for now, but if it ever gets obsoleted, I think I can use your device to get a DD optical feed from a new Roku.
I don’t know if it helps the OP, but this is a cool device.



