If there is no audio through USB then why does my Nova 5x come with a dongle which plugs...

If it's an "off the shelf" Bluetooth dongle, then no.

In order to work, an USB device needs specific drivers, so the computer or console knows which kind of data is coming in through the USB Port.

Since you can't install additional drivers on a Xbox console, you'll have to live with those drivers that come with the console, and that is without a basic Bluetooth stack.

So no, you can't simply plug in a Bluetooth dongle hoping the headset will work.

You will need specific Xbox Licensed headsets to work wireless on the Xbox One. Or simply get a standard 3.5mm headset and connect that to your wireless controller.

Or get a wireless headset that has it's own wireless base station that connects to the physical audio output of the Xbox One (i.e. optical TOSLINK), and gets power through the USB Port. But currently, no audio is put out via USB. Then the headset's base
station transmits the sound via it's own proprietary wireless protocol, or if the Base Station supports it, Bluetooth.

the xbox does not support audio over usb, only for a very small select of headphones that have dongles.

there are limited headsets that will work via a specific dongle for usb on xbox, all other usb headsets are not supported in anyway as the xbox does not output audio via usb normally.

My son had this problem. His wireless headset did not connect directly to the Xbox, he needed to plug in a littl USB dongle that came with the headset into the xbox for it to work. Make sure you don't need one of these USB dongles for it to work and if
it does, maybe try a different USB port on the xbox.

I can already plug a bluetooth dongle into my PC and windows 10 will find the controller as a bluetooth device, which i can then use to stream the xbox to a PC. But my network is poor, the video quality is low and there is too much latency.

So why on earth cant Microsoft install a patch on the xbox to allow a bluetooth dongle plugged into the USB port of the xbox to do the same? At least then i can use a USB extender cable with a bluetooth dongle to get my controller range extended to where
i need it. Its running the same OS as the PC under the hood is'n't it!!!

This is a BIG problem Microsoft, and i will be buying playstation next time if this isn't addressed.