sound – Ubuntu 20.04 Dual Boot snd_hda_intel Audio Buzzing

I recently installed 20.04 alongside W10 on a Dell Inspiron 15 3501 and there’s a buzzing sound alongside all the audio. It sounds like all sound is coming from inside a nested pair of tin cans, much like a lot of the audio in Half-Life. It also resembles the buzzing of a CRT screen.

Best progress so far: I installed alsa-utils and played around with hdajackretask. It shows two codecs, one called “Intel Tigerlake HDMI” which has a bunch of “Digital Out, HDMI” pins. Setting a certain one of these to “not connected” (fig. 1) has caused the sound to reliably come out clean from YouTube. However, voice chat apps, system sounds, and -most bafflingly- Deezer (also in browser!) still have the buzz. Playing around with various configurations has caused these to work at one time or another, but then it stops working with the same config, so I’m pretty sure it’s a fluke. Only YouTube is reliably fixed.

Note that it’s the same through laptop speaker and headphones. It’s not present on bluetooth.

The other codec is “Cirrus Logic CS8409/CS42L42” which seems to be the actual sound card, but I haven’t seen any changes overriding things there.

I also reinstalled the drivers by reinstalling linux-sound-base alsa-base alsa-utils, nothing has changed.

I’ve also tried pavucontrol, messing with all sorts of ALSA settings, turning off the power save in alsa-base.conf, and I think just about everything except reinstalling the OS. All dependencies for the snd_hda_intel driver are installed, none of the diagnostic commands I’ve been advised to try have shown anything not working, everything is fine on Windows, and the sound on Ubuntu is quite good apart from that damn buzzing. Anyone have another idea? I ran that ALSA script which prints all possible diagnostic data, it’s here but I don’t know how to interpret it.