I had a bug similar to this for years. I tried multiple distros, DEs, hdmi cables, display port cables, etc etc. I didn’t want suspend, but I really need screen blanking. I finally had a revelation deep in some forum somewhere that mentioned some feature on my monitor. I forget what it was exactly, but it was an ‘auto’ something that prevented the computer itself from doing anything.

Odd, but possible.

In Linux I always use sound converter. Works great.