I found a USB Bluetooth adapter when going through the heaps of various equipment I am hoarding, and my first thought was: I will plug this to HA, but then what?
My question: what are your uses (if any) for BT attached to your HA server, in a generic place (in my case, more or less in the center of the apartment, on the top shelf of a closet)
Room level presence detection with Bermuda.
Besides bluetooth in my closet I own several esp’s around the house serving as bluetooth proxy. They relay information from bluetooth curtains, thermometers, plant sensors, trackers, toothbrushes and, believe it or not, a showerhead. Since the esp’s and the bluetooth adapter are all over the place, I’m also experimenting with the Bermuda integration, which locates in which room certain bluetooth devices are by seeing which esp is closest. I have not yet caught the showerhead secretly leaving the bathroom 
Have you tried this product?
@Spiro this thread is gold.
Then you definitely need Bermuda to see who took the shower and forgot to return it 
Your first thought should have been: Is this adapter even on the supported bluetooth adapter list in the HA integration, or am I just wasting my time? 
The Bluetooth adapter could be used in relation to Matter and commission of devices directly through the HA server, which require a dedicated USB adapter for the Matter server.
Even if it is not supported, I would use the opportunity to get a supported one if there are interesting uses (and they are, apparently)
While I don’t see a huge amount of value in using your HA server as a ble scanner these days (with ESPHome covering that well), I was using something similar to actively scan for my phone’s traditional Bluetooth (not BLE) based on hallway motion and apartment door events as part of my overall faster home arrival/departure detection strategy.
Unfortunately it’s not available on HA OS any more.
This integration is only available on Home Assistant Core installation types. Unfortunately, it cannot be used with Home Assistant OS, Supervised, or Container.
I then moved this approach to Monitor, which also has waning support, but also can leverage traditional Bluetooth via a pi zero or other device.