- https://www.youtube.com/watch?v=xuAMNWlmoh0
- https://mostechtips.com/solved-cant-remove-bluetooth-device-in-windows-10/
When being asked for a keyboard PIN (when there isn’t one) remove the exceptions DB from:
HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Bluetooth
When you simply can’t remove an existing device through any means at all, remove the Bluetooth controller and reboot many many times. You might get lucky.