I was wrong about the BIOS - there is no option for disabling HDMI audio there. So, it's just not working because I'm likely missing the needed module.
I took a look at the wiki page about nvidia audio. My MD does not output the same info:
lspci -vv
01:00.1 Audio device: nVidia Corporation Device 0be3 (rev a1)
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
Latency: 0, Cache Line Size: 32 bytes
Interrupt: pin A routed to IRQ 10
Region 0: Memory at fe97c000 (32-bit, non-prefetchable) [size=16K]
Capabilities: [60] Power Management version 3
Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
Status: D0 PME-Enable- DSel=0 DScale=0 PME-
Capabilities: [68] Message Signalled Interrupts: Mask- 64bit+ Queue=0/0 Enable-
Address: 0000000000000000 Data: 0000
Capabilities: [78] Express (v2) Endpoint, MSI 00
DevCap: MaxPayload 128 bytes, PhantFunc 0, Latency L0s <4us, L1 <64us
ExtTag+ AttnBtn- AttnInd- PwrInd- RBE+ FLReset-
DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
RlxdOrd+ ExtTag+ PhantFunc- AuxPwr- NoSnoop+
MaxPayload 128 bytes, MaxReadReq 512 bytes
DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend-
LnkCap: Port #0, Speed 5GT/s, Width x16, ASPM L0s L1, Latency L0 <512ns, L1 <1us
ClockPM+ Suprise- LLActRep- BwNot-
LnkCtl: ASPM L0s L1 Enabled; RCB 128 bytes Disabled- Retrain- CommClk-
ExtSynch- ClockPM+ AutWidDis- BWInt- AutBWInt-
LnkSta: Speed 2.5GT/s, Width x1, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt-
aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: default [USB PnP Sound Device ], device 0: USB Audio [USB Audio]
Subdevices: 1/1
Subdevice #0: subdevice #0
aplay -L
front:CARD=default,DEV=0
USB PnP Sound Device , USB Audio
Front speakers
surround40:CARD=default,DEV=0
USB PnP Sound Device , USB Audio
4.0 Surround output to Front and Rear speakers
surround41:CARD=default,DEV=0
USB PnP Sound Device , USB Audio
4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=default,DEV=0
USB PnP Sound Device , USB Audio
5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=default,DEV=0
USB PnP Sound Device , USB Audio
5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=default,DEV=0
USB PnP Sound Device , USB Audio
7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=default,DEV=0
USB PnP Sound Device , USB Audio
IEC958 (S/PDIF) Digital Audio Output
null
Discard all samples (playback) or generate zero samples (capture)
The alsamixer doesn't show anything muted.