Surround Mixing With HDMI?

The amp in my surround system (Gigaworks S750) recently died, so I’m hunting for a replacement solution. The ideal scenario might be to connect the HDMI from my PC’s GPU to an AVR, but I’ve only been able to find hearsay about whether the discrete HDMI audi channels can be accessed for mixing.

Can anyone please confirm whether Cubase can see the separate HDMI channels? And if not directly in Cubase, can it be achieved via something like Asio4All, or even in other apps like Davinci Resolve?

Latency isn’t a concern, as I would only be using the HDMI for mixing.

Thanks for any help!