My day job is building widgets that connect to a windows PC over Bluetooth. The situation is so bad that we're building a dedicated RF adapter so we can have a sane stack under our control.
If your program is scanning for a particular device in the background, that device will never show up in the windows BT pairing menu. I can't even imagine how that happens. Many API calls do nothing or return garbage, many BT features are just not exposed at all, despite windows clearly having that data internally.
W10 never even had BT audio sink. You could not play audio from a remote device to your PC. W7 had it and I think W11 finally got it a few years back. Linux has always had it.
Windows' Bluetooth stack is no contest the worst available on the market. It's astonishing how poor quality Microsoft products are these days.
Stereo is just dual mono. its that simple. Summing is just math, its that trivial.
Creating a mix of multiple inputs for a stereo lr output? also completely trivial from a technical standpoint. Hardly trivial from a creative pov, but that isnt what this is about.
But in general Bluetooth is just bad protocol audio...
Is it much better than 10 or 20 years ago? Yes.
Is it still annoying enough and sometimes colossal waste of time? Yes. Just use a Macbook and be done with it.
Asus laptops have always worked flawlessly for me.
I am writing this on an Asus laptop with linux mint. Everything just works perfect out of the box.
I could buy three of these laptops instead of the same setup on a mac is the major selling point for me.