Okay, so you have a few things going on here, but it’s hard to get specific about what the actual issue here due to the number of variables. Here are some places to start looking:
alsamixer (cli) or pavucontrol (gui) will have a lot of easy to configure options for your audio setup. Have a run through those.
this sound card seems to have hardware audio controls that can be problematic while dual-booting Windows, so make sure you have fast boot disabled on Windows, and boot your Linux side twice in a row after turning it off to be sure the state of your devices is cleared
Your audio profile is only half of the equation due to the hardware controls on the card. The port modes need to be set ON the card, as well as power for channels (possible the card does this automagically)
Essentially, if you have a hardware controlled 5.1 cars, it’s natural state is probably going to be…5.1. so your first job is telling the CARD what mode it should be in, which should be 2.1/3 in your case. What you’ve done so far is just set an audio output profile for the speakers, which isn’t quite the same thing. Check alsamixer or pavucontrol to try and sort this out.
Next step if the above doesn’t work: dig into getting mode and config info from the card itself. The amixer command will be helpful here. If this is the only audio card in the machine, try ‘amixer --card=1’ (it might be 0), and see what info it has.
Past that, you should be on a path to find a working config. If all else fails, I’m betting you can get a solid hardware controlled card online for dirt cheap, maybe with a chipset that has full or better Linux support.