HDMI output only works after display goes to sleep

[nitro322]

I've run into one of the weirdest issues I've encountered in quite a while. I'm up a new computer, and generally get no sound through HDMI (PCH works fine), but noticed that if the display it's connected to goes to sleep and then I wake it up again, audio starts working through HDMI. Reboot or changed the device or whatever and I get silence again, but wait for the display to go to sleep and then I get sound again. Discovered it the first time by accident, repeated it twice more to confirm it's a consistent behavior.

Additional background:

• I'm setting up an Intel Tiger Lake NUC (Panther Canyon) with the new Xe graphics. I'm not sure if or how much the fact that it's relatively new matters.
  
• My initial setup failed because the i915 DRM video driver wouldn't load the needed firmware; after some research I discovered that a built-in driver requires initrd for firmware loading, so I changed the i915 driver to be a module. That got video working.
  
• I then noticed that my audio devices disappeared. Eventually discovered that the i915 driver needs to be loaded prior to the HDA driver, so converted the sound drivers to modules as well.
  
• Next discovered that my sound devices still weren't loading properly, and after much trial and error I found that snd-hda-codec-hdmi needed to be loaded before snd-hda-intel to populate all the sound devices correctly. Don't know why, just rolling with it at this point.
  
• I tried upgrading to kernel 5.12.6 just in case there was a driver issue with the stable kernel, but made no difference. Tried toggling a bunch of the ALSA options on and off (silent stream, dynamic codec reconfiguration, even disabling the non-HDMI codec for my card (realtek), but still no difference.
  

Before I start spamming my kernel config, alsa devices, /proc/asound/cards, pactl output, etc., wanted to post an overall summary. Has anyone seen this before? Any suggestions on where to go from here? I looked into upgrading pulseaudio as I've seen others mention compatibility issues with 13.0 and modern hardware, but that doesn't seem to be an option at this time. Not sure if that's my problem anyway.

Happy to provide any additional details or output, just let me know. Been at this about 6 hours now and pretty much out of ideas.
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[nitro322]

Gave up on pulseaudio and fell back to ALSA, which I was using on the system this replaced. I can get sound initially working, but bitstream passthrough generally does not. It'll play basic AC3 fine, but DTS or any newer format results in silence, and once it enters this state I need to reboot again.

This is replacing a much older NUC w/ working everything, so I know my receiver/speakers/tv are all perfectly capable, and ALSA can work. No idea why it's so jacked up now other than a driver issue, but tiger lake support has been included long enough I'd expect major breaking bugs like this to have already been caught and fixed.

Guess I'll try figuring out how to upgrade to pulseaudio 14 and see if that has any positive effect. I think passthrough worked with it, after that stupid sleep/wakeup thing.
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