As for compatible headphones, Microsoft says shared audio in Windows 11 works with a wide range of accessories that support Bluetooth LE Audio. Those include (not limited to) Samsung Galaxy Buds2 Pro, ...
If you have two headphones, speakers, earbuds, or any other Bluetooth hardware, you can now use both simultaneously on a Copilot+ PC.
The Bluetooth LE-based feature will allow testers to broadcast audio across wireless headphones, speakers, and hearing aids.
Windows 11 Insider build 26220.7051 adds shared audio (preview), letting Copilot+ PCs stream sound to two Bluetooth LE Audio devices.