Please support virtualbox-kvm on Linux

[VanNostrand]

On https://github.com/cyberus-technology/virtualbox-kvm there is a patch for the VirtualBox code that allows Virtualbox to use KVM on Linux. It is a pre-release but works quite well - except in combination with Vagrant there are some issues:

• vagrant up does not create a VM because Virtualbox-KVM prints the original error message that the VirtualBox modules are not loaded. This is true but Virtualbox-kvm does not use these kernel modules. Vagrant seems to parse the output for these messages and does not create the VM.

The provider 'virtualbox' that was requested to back the machine
'default' is reporting that it isn't usable on this system. The
reason is shown below:

VirtualBox is complaining that the kernel module is not loaded. Please
run `VBoxManage --version` or open the VirtualBox GUI to see the error
message which should contain instructions on how to fix this error.

• I still had a VM from my old Virtualbox & Vagrant setup, so I tried to start it manually from Virtualbox itself. This VM was not able to start without configuration changes; I had to change the hardware drivers from the standard ones (AHCI, Intel Pro 1000, Legacy Paravirtualization) to their kvm counterparts (virtio-scsi, virtio-net and KVM paravirtualization interface) in the VirtualBox gui and I had to change the networking from bridged network to NAT to be able to boot the VM (yeah, that setting comes from the Vagrant file below).
  Not sure if "vagrant ssh" will work without the bridged network though, but I cannot test in the current state and I am not sure if that is more a vagrant or more a virtualbox-kvm issue.
  The readme file of virtualbox-kvm says

The new KVM backend utilizes the --driverless mode of VirtualBox. Some setups that require kernel module support will not work in this mode and prevent the VM from starting. Specifically, the Bridged adapter and "NAT Network" modes do not work. Only regular NAT is easily supported. More complex setups will need manual configuration, e.g., using tun/tap devices.

Vagrant version

Vagrant 2.4.0

Host operating system

Gentoo Linux with kernel 6.7

Guest operating system

The official opensuse/Leap-15.5.x86_64 from vagrant cloud

Vagrantfile

Vagrant.configure("2") do |config|

  config.vm.box = "opensuse/Leap-15.5.x86_64"
  config.vm.hostname = "seminar"

  config.vm.network "public_network", bridge: "eth0"

  config.vm.provider "virtualbox" do |vb|
     vb.gui = true
  end

  # that just installs packages, it is active in my Vagrantfile but irrelevant for this issue:
  #config.vm.provision "bootstrap", type: "shell", inline: "/vagrant/bootstrap.sh"
end