my 7.1 AVR does not support Dolby HD/TrueHD Atmos 7.1 through ARC passthrough. unfortunately, when turning off passthrough, the channel mappings are wrong: for any speaker configuration >5.0 there's no sound from the front speaker.
the debug log seem to indicate that the front center (FC) and subwoofer (LFE) are switched:
15:03:06.719 T:4085248912 DEBUG: CAESinkALSA::SelectALSAChannelMap - Selected ALSA map "FL FR LFE FC RL RR RLC RRC"
15:03:06.720 T:4085248912 INFO: CAESinkALSA::InitializeHW - Your hardware does not support AE_FMT_FLOAT, trying other formats
15:03:06.720 T:4085248912 INFO: CAESinkALSA::InitializeHW - Using data format AE_FMT_S32NE
15:03:06.748 T:4085248912 DEBUG: CAESinkALSA::GetChannelLayout - Input Channel Count: 8 Output Channel Count: 8
15:03:06.748 T:4085248912 DEBUG: CAESinkALSA::GetChannelLayout - Requested Layout: FL, FR, FC, LFE, BL, BR, SL, SR
15:03:06.748 T:4085248912 DEBUG: CAESinkALSA::GetChannelLayout - Got Layout: FL, FR, LFE, FC, SL, SR, BL, BR (ALSA: FL FR LFE FC RL RR RLC RRC)
15:03:06.748 T:4085248912 DEBUG: CActiveAESink::OpenSink - ALSA Initialized:
15:03:06.748 T:4085248912 DEBUG: Output Device : AML-M8AUDIO
15:03:06.748 T:4085248912 DEBUG: Sample Rate : 48000
15:03:06.748 T:4085248912 DEBUG: Sample Format : AE_FMT_S32NE
15:03:06.748 T:4085248912 DEBUG: Channel Count : 8
15:03:06.748 T:4085248912 DEBUG: Channel Layout: FL, FR, LFE, FC, SL, SR, BL, BR
15:03:06.748 T:4085248912 DEBUG: Frames : 2048
15:03:06.748 T:4085248912 DEBUG: Frame Size : 32
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(the problem seem to happen on all multichannel audio formats, not just Atmos streams - but my AVR supports the other formats via passthrough)
this is on a 905x (mecool m8s pro plus) using the 8.90.4 build.