Hyper-V and VirtualBox in Windows Server 2022 Standard
To make VirtualBox compatible with Hyper-V, you need to activate "windows hypervisor platform".
In most windows OS versions, this is a feature you turn on by using "Turn windows features on or off".
However,the feature "windows hypervisor platform" is missing on the Windows Server 2022 Standard manager UI!
Open a CMD as an administrator
Write command Dism /Online /Enable-Feature:HypervisorPlatform