Thanks. That helped a lot. It gave me a good basis for some further googling.
It ended up that the Internal Clock of the hardware interface was deselected in alsamixer. Enabling it fixed the no audio issue.
For the channel remapping I tried a bunch of different config files until finally one actually managed to not be ignored. It’s absurd how many separate configuration files and sound settings menus exist for linux audio and there’s no guarantee the one your editing is even being used. An absolute mess IMO and it’s no wonder people shy away from linux for desktop purposes.
Funny enough, despite getting the channel remapping to work, it’s completely ignored unless you put pulseaudio -k into your user profile. And even now, because the remapped output device doesn’t show up on boot, it has to be manually set to the default output every login.
At least I have the right channels mapped though.
I love linux but god damn is it a hot mess for the simple stuff.