Just wanted to note that I'm still having this issue with the latest drivers released yesterday, AAF DCH Optimus Sound 6.0.9175.1 (Signed), both with the Legacy and Universal drivers.
I can't seem to get anything other than 2-channel functioning properly in applications, whereas I know S/PDIF does support 5.1 as it was working before the latest Windows 21H1 update. I am not able to find the settings that TheDoctorTash recommends, but also this is not a problem with just browsers, but the audio device usage throughout the OS.
Oddly though, when I go to the "Supported Formats" tab of "Additional Device Properties" in Windows (Win key -> "Sound Settings" -> Device Properties -> "Additional Device Properties" on the right -> Supported Formats tab) and click Dolby Digital and then Test, I get sound in all 5.1 channels, starting with the subwoofer and moving from Front Left speaker all the way around to Rear Surround Left speaker, each speaker only making sounds for its specific channel test. This tells me the system and the driver currently should support 5.1 functionally, but in terms of what the OS being told out output by applications, it is adhering to the the 2-channel, 16 bit option selected under the Advanced tab, shown in the screenshot.
Any assistance on what I'm possibly installing or not installing that would allow me to get that 5.1 option would be great. My home theater setup is sad without its 5.1 configuration.
Edit: I finally went back to a download from January, AAFAudioPackDCH-6.0.9079.1. This release had the colorful AAF splash while the installer was loading. This release, using the Legacy drivers with the both DDL and DTS drivers, works perfectly. See the second screenshot for proof.
Thanks for any and all help in investigating this!