^new^ - Netflix Surround

Mobile devices default to stereo to save bandwidth. Casting to a TV may reactivate surround.

Yes, but separately: “Netflix Spatial Audio” (available on Premium plan) works with any stereo headphones, simulating 5.1 or Atmos. It is not true multichannel but can be effective. netflix surround

Yes, but only when system audio is set to “Dolby Atmos” (requires HDMI to Atmos AVR). Mobile devices default to stereo to save bandwidth