Steam Deck 5.1 or 7.1 sound doesn't work. It works using https://github.com/mariotaku/moonlight-tv on the same host

[vrokolos]

So my steam deck is configured correctly in desktop mode it has 5.1 setup or 7.1 setup and testing it works perfectly from the audio settings.

Windows Host is also configured correctly for 5.1 or 7.1 sound.

Testing streaming using moonlight on steam deck from both game and desktop mode: everything is Left and Right only.
Testing streaming using LGTV https://github.com/mariotaku/moonlight-tv with same host options / sunshine version 5.1 works perfectly on the same TV.

[MajinChibi]

ValveSoftware/SteamOS#1639

Seems to be a bug with Steam OS.

When you play a native steam game on the deck, do you get 5.1 in Game Mode?

[MajinChibi]

There is now a workaround!
ValveSoftware/SteamOS#1639 (comment)

must apply in desktop mode:

"In the folder /etc/pipewire/pipewire.conf.d you will find 4 filters/virtual sinks.
filter-chain-sink.conf
filter-chain.conf
virtual-sink.conf
virtual-source.conf

If in the user directory of /home/deck/.config/pipewire/pipewire.conf.d you create blank text files with the same names as the ones above and then reboot, it overrides the Pipewire config and these virtual sink and filter chain devices disappear. Then your device will correctly send the right number of audio channels"