Samsung defaults the signal out to Dolby Digital, rather than detecting the method. They may do this because the most common use case would be to connect to a sound bar.
So this is most likely specific to Samsung.
Connect Optical Cables to TV and to the Optical to RCA Adapter
Connect the USB power cable to the Optical to RCA Adapter and the other side (USB-A) to the TV in an unused USB Port.
If there is no sound, please take a moment to make sure all the connectors are connected properly. If it is confirmed to be properly connected but there is still no sound, use the following steps to verify the TV Settings.
From the TV Remote:
Click SETTINGS button on Remote
Confirm Sound Output set to AUDIO OUT/OPTICAL. If it is not selected, then press ENTER Button and select Audio Out/Optical
Select EXPERT SETTINGS
Confirm Digital Output Audio Format is set to PCM. If it is not selected, then press ENTER Button and select PCM.