Decklink Mini Recorder 4K - 7.1 audio help?

Hello!

I recently picked up a Decklink Mini Recorder 4K because I was under the impression that it supported 8-channel audio capture via HDMI. I updated the Decklink's firmware via USB, and installed the latest version of the Desktop Video Setup app (which recognized the device). However, no matter what I do, Windows 11 only recognizes the DeckLink as a stereo audio input device -- which is also reflected in OBS and Adobe Audition.

The user manual BlackMagic provides doesn't discuss the Mini Recorder 4K specifically, and according to what I've been able to find online, there aren't any additional setup steps needed to get up and running. Am I missing something?

Any advice on this would be greatly appreciated; I've been troubleshooting this for weeks!
My computer's specs and a status report from the Desktop Video Setup app can be found below:

Device Info:

Decklink Mini Recorder 4k
Persistent ID: 14360413
Video Input: HDMI 1080p59.94, 8-bit BGRA
Video Options: Capture 1080p as PsF - Disabled
Device Interface: PCI
PCIe Status: Link Width 4x / Link Speed 5 GT/s

System Configuration:

Mobo: HP 89B5
Physical Memory: 8262 MiB
Operating System: Windows 10.0.22631
Physical Processors: 8

CPU: Core i3-12100, 3.3Ghz, 4 cores
RAM: 8gb
GPU: Intel UHD 740 (had to remove my video card to free up a PCI slot for the Decklink)
OS: Windows 11