Bluetooth via a hdmi dongle?

My desktop PC doesn't support Miracast, so I cannot use a bluetooth headphone, I have confirmed this! But I have been told that you can buy a Miracast adapter (sometimes called a dongle) that plugs into an HDMI port.
My question is this: Does the dongle plug into a spare hdmi connector on my motherboard, just as you would connect an internal hard drive? I have no other hdmi connectors on my desktop PC.

Any advice would be welcome.

Windows 10 home clean install, latest version 1903 64 bit. 6 core 3500 mhz 32 gig ram.

If you wish to use a Bluetooth headphones with your PC you need a Bluetooth "Dongle which connects via USB.

Miracast is a method to wirelessly display the contents of your PC screen on another Screen (usually a TV)

They are not as far as I know related

Yep...as Barman58 stated, miracast and Bluetooth have nothing to do with each other.
Miracast - What is Miracast?

All you need for bluetooth is a bluetooth USB dongle (adapter).
Bluetooth USB Adapters, Bluetooth Dongles - Newegg.com

Most Bluetooth 'dongles' are for a USB port. I use this one in a Dell Latitude E6410 Notebook that does not have the built-in Bluetooth [usually is part of the Wireless/Wi-Fi adapter]:
https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1
I usually keep a couple on hand, should have replacements tomorrow.

Your iMac and most other models of Mac come with Bluetooth built in, convenient since the separate desktop keyboard and mouse use it. Their Notebooks also have it, I used a Microsoft BT mouse with my MacBook Pro for several years until the Notebook decided to die, now use the mouse on Windows.