Unknown Bluetooth connection

To identify and remove the mysterious Bluetooth device from your iPhone, look for a small information icon (i) next to its name in your Bluetooth settings, which allows you to select "Forget This Device." Cryptic names containing a long string of letters and numbers are usually MAC addresses (unique hardware identifiers) displayed because the device hasn't fully shared its broadcast name with your iPhone yet

Try this

• Check the icon: Look closely at the icon next to the cryptic name in your Bluetooth list. iOS often displays a specific icon (like a headphone, watch, or speaker) even if the name is just text and numbers.
• Look up the MAC address: If the name looks like a 12-character hex code (e.g., 00:1A:7D:DA:71:11 or A1-B2-C3-D4-E5-F6), copy it. You can paste it into a free online MAC OUI Lookup tool to identify the manufacturer of the device (e.g., Apple, Sony, Tile, or a smart home brand).
• Cross-reference your apps: Many smart gadgets (fitness trackers, smart bulbs, or tracking tags) connect via Bluetooth Low Energy (BLE) directly through a companion app rather than your standard iOS Bluetooth settings.

Without the info button to disconnect, then it is an App that you have installed on your device managing the connection because you have allowed it at Settings > Privacy & Security > Bluetooth. Go to that location and turn off the permission one by one and when you have found the correct app, that device will no longer be showing in your Bluetooth list.

Once the app is identified, then it should be clear what device that is. You can either remove it from the app, remove the app, or remove permission for the app to use Bluetooth.