After many tests and additional discussion with @Agoldnear in another thread regarding my specific Sony receiver, the conclusion is that the receiver indeed doesn’t accept DSD 5.1 over DLNA, but does only over HDMI and USB stick/files.
It accepts PCM 5.1 over DLNA, so to play the multichannel track, it has to be converted before it is sent to the receiver.
To play the stereo track of a SACD/DSD, the Auridvana Origin output needs to be set to stereo in the settings in order to force reading the right track and not sending the 6-channel one.