From bleepingcomputer.com
Microsoft removed a compatibility hold caused by outdated Realtek Bluetooth drivers and published a support document describing a workaround designed to help Windows 10 users still affected by the safeguard hold.
Users of still impacted devices will receive a “Realtek Bluetooth: Your PC has a driver or service that isn’t ready for this version of windows 10. A new version is available” error message when attempting to update to Windows 10 version 1909, version 1903, or version 1809.