I can't find that term in the SDK docs, where do you get that info from? google suggests that term is something to do with https://www.vmix.com/
You are correct, I mixed it up, I am currently playing it with vmix and only that option gives all channels.
Not that you need it, but here is the DeckLink SDK manual:
https://documents.blackmagicdesign.com/UserManuals/DeckLinkSDKManual.pdf?_v=1734595211000vmix doesn't have flexibility of Rendering and filters, that is why I would like to go back to MediaCenter.
Good news is that 2 channels it captures are L/R, not a downmix, which means others are just offset to it.