With both stable and nightly (23-02-2020) passthrough is not working correctly. In Coreelec I have set the audio output and passthrough device to ALSA;AML-AUGSOUND,HDMI - but PCM 2.0 is being sent out for everything except Dolby 2.0. (Its always correct). The amp works fine with my sat box and Panasonic UB820.
Tested with AAC 2.0, Dolby HD 5.1, Dolby HD 7.1, DTSMA 5.1, DTSMA 7.1, Dolby HD 7.1. Normal Dolby 5.1 is sometimes sent out correctly and sometimes as PCM 2.0