https://www.bleepingcomputer.com/news/microsoft/microsoft-removes-windows-11-update-block-for-virtualbox-users/

Microsoft has removed the last Windows 11 safeguard hold after Oracle addressed a known VirtualBox issue causing errors and virtual machine start failures when Hyper-V or the Windows Hypervisor were installed.

Safeguard holds prevent users from upgrading to Windows 11 to protect their systems against potential upgrade issues, in this case, software instability caused by compatibility issues between Windows and VirtualBox.