Thanks for the suggestion, but I don't think we will ever explicitly add support for this to the UI. virt-manager will never explicitly target virtualbox, even if libvirt supports it. We really aim to only target native virtualization like kvm, xen, lxc.

Of course, if you use virtualbox with virt-manager and everything is broken, we should consider fixing those issues. But it's never going to be an advertised option

Why so?

virt-manager -c vbox:///system
or
virt-manager -c vbox+ssh://username@host/system

seems to work just fine - why not expose it in GUI?

For the reasons I mentioned above: we only aim to target native virtualization. It's the same reason we don't expose any of the vmware drivers in the UI. For people that are sufficiently motivated, they can use the workaround you suggest.

I thought pure qemu (non-kvm) VMs are supported as well. So it's not like you're afraid to support competitive product from Oracle - it's purely philosophical difference :)

uh, no, it has nothing to do with competing product. we advertise xen as well which RH hasn't pushed for like 5 years.

the reality is that 99% of virt-manager usage is qemu/kvm, xen, or lxc. listing every libvirt driver in the UI would be distracting from our primary use cases, and would give the incorrect impression that these bits are regularly tested with virt-manager.

https://www.virtualbox.org/ticket/1019 - for the sake of completeness, here's the link to corresponding bug in virtualbox where devs expressed the same 'we don't give a crap' attitude.