We are talking about multiple problems.
If Netflix only sends two channels, you're not going to be able to play it in 5.1. That has nothing to do with Microsoft. If you buy a Volkswagen, you can scream at VW all day long, but you're not going to be driving a Lamborghini anytime soon.
Your problem sounds way different.
Did you clean out the SB drivers between running totally different hardware?
If you pull the diesel engine out of your VW and put in a Peterbuilt diesel, you're not going to get any wheels to spin.
I've tried all of the hardware you have, except for the Xonar, and they all work fine with all 5.1 channels on Win 7 through Win10. But I'm careful how I install my drivers. Not saying you aren't, but something doesn't sound right.
Driver problems 'sort of' are a Windows problem in that they'll get with the HW manufacturer.
It's like Volkswagen sitting down with your gas station and explaining too them how Octane works.
But sure, blame MS. See if you get that Peterbuilt engine working anytime soon. Meanwhile, I'm driving an SLK 55 with the original 5.4L engine and it's working great.
Except for Netflix. They only send 2 channels.