The latest Ubuntu release uses a desktop system that's not quite compatible with VirtualBox's built-in tools, but there's a command line fix, as explained by the Unixmen site.

Each Linux system will be slightly different, but the Tombuntu blog's instructions for installing VirtualBox Guest Additions in Ubuntu hold mostly true: head to where the ISO is mounted as a CD ...

If Seamless Mode option is grayed out or not working in VirtualBox, you need to install Guest Additions image and disable 3D Acceleration.

If VirtualBox displays a black screen & is not booting the guest OS or not opening the installation window, you need to disable Hyper-V and 3D Acceleration.

Learn how to run Windows on Linux using VirtualBox. This step-by-step guide covers setup, optimization, and seamless integration.