Trying to record stereo mix on ALC892 HDA

Howdy! I am trying to get a livestreaming setup where I can hear my 
microphone and line in at the output (zero latency monitoring) and also 
record the stereo mix (record what I hear). I have achieved this on 
Windows, so I know the hardware can do it, and now I'm trying to achieve 
this on linux. When I configure it on windows, the stereo mix appears as 
an extra input.

I've managed to get the monitoring to work, but can't manage to record 
the stereo mix.

I've tried various combinations of flags in the hint file, sometimes I 
can see Stereo Mix as the source for the two DACs, and sometimes not. 
When I select it, there is no signal coming in, even though I'm playing 
some sounds.

I am not sure what to try next. I don't understand what pins are, I've 
tried hda-analyzer and it's not clear to me what flags I need to set. 
Maybe I can take the config from windows and copy it to linux somehow?

Is there a driver flag that creates the stereo mix as an extra input?

I don't want to use software options like using the pulseaudio monitor 
source, because that wouldn't have the mic mixed in, and I want to 
monitor the mic volume relative to the desktop volume, essentially to 
record what I hear exactly as I hear it.

Thanks in advance!

/etc/modprobe.d/hda.conf:
options snd-hda-intel power_save=0 patch=,hda-hint.fw

/lib/firmware/hda-hint.fw:
[codec]
0x10ec0892 0x14629b86 0

[hint]
#add_hp_mic = yes
add_jack_modes = yes
add_stereo_mix_input = yes
#mixer_nid = 0
#auto_mic = no
auto_mute = no
#hp_mic_detect = no
indep_hp = yes
jack_detect = no
line_in_auto_switch = no
power_save_node = D0
#multi_cap_vol = yes