Making use of Linux’s Kernel-based Virtual Machine (KVM) opens up new possibilities while users can still enjoy the VirtualBox VMM itself. The KVM support is part of the mainline kernel so there is less worries with not having to use the VirtualBox kernel driver, KVM tends to support new features quite quickly, and tends to be more actively developed than VirtualBox and is embraced by a range of organizations. Early users of this backend by Cyberus customers are said to be experiencing better performance too.
hope this helps with the dumbster fire of the virtualbox version in the official Ubuntu repositories
(virtual box basically “breaks” on Ubuntu LTS once a newer HWE kernel gets released unless you install a newer version of it, leading to hundreds of support threads every time this happens)