I have a Mecool KM2 (Android TV version 10) with optical SPDIF audio output connected to Logitech speakers with Dolby Digital/DTS decoder support. When the HDMI output is connected to my TV, 5.1 audio passthrough works fine, to HDMI as well as to SPDIF. When the HDMI output is connected to my beamer without audio (or not connected to anything for that matter), the SPDIF sound is only PCM stereo.
I configured the supported sound formats manually in the sound menu, but that does not help, it seems the SPDIF output only works in passthrough if the connected HDMI device supports it.
What am I doing wrong ?
If the device has an SPDIF option then that's what you need to select in the audio settings, those boxes have the option in a separate menu, look for it, select it then try again.
The SPDIF option works independent of what the TV supports when using HDMI.
Let me know what happens.