Comment # 2 on bug 1184074 from Andrea P

(In reply to Takashi Iwai from comment #1)
> It's likely due to the HDMI silent stream that conflicts with the
> (non-working) Nvidia HDMI audio.  The kernel config was turned off recently,
> but I guess it's not propagated to the released kernels yet.
> 
> As a workaround, add the boot option
> snd_hda_codec_hdmi.enable_silent_stream=0

Thanks for your quick reply.
Unfortunately the boot option doesn't solve the issue.
I'd also like to add some new information: my thoughts were that something got
corrupted having previously installed via Nvidia output, so I tried to
re-install a full new TW installation in an external SSD using the HD530 only.
This has not been solve the issue either. So, I guess it's something related to
my iGPU. The nvidia has no blame, apparently :)