Virtualbox is not your only option if you want to use Vagrant. Vagrant has decent plugins for qemu (vagrant-libvirt) and lxd (vagrant-lxd)

Make sure you get your KVM, Qemu and libvirt setup right and run:

    vagrant plugin install vagrant-libvirt
    vagrant init generic/ubuntu1804
    vagrant up --provider=libvirt

You can export VAGRANT_DEFAULT_PROVIDER=libvirt to avoid passing --provider=libvirt to vagrant all the time.

vagrant-lxd is less mature but just as useful, especially when you need to run stuff with erratic RSS graphs.