I have been using VirtualBox for years to manage my virtual machines (including Vagrant). It always worked fine, but with over 150MB in size, it felt a little on the heavy side.

Today I looked into Qemu again. In the past I found it too complicated to get to work, but these days virt-manager provides a familiar GUI. I got PureOS working in no time flat. As Qemu uses KVMs (or Kernel-based Virtual Machine) it is neatly integrated with the Linux kernel, with all the advantages that that brings. Like less than 50MB for the combo of Qemu/virt-manager.

And to top it all off, libvirt can also be used as a Vagrant provider.