Last time I checked (months ago) VirtualBox just couldn't run under Hyper-V. If you Google around you'll see lots of threads, e.g. https://superuser.com/q/1208850
Apparently they claim that as of February 19, 2020, they've "Restored the ability to run VMs through Hyper-V, at the expense of performance". https://www.virtualbox.org/wiki/Changelog-6.1
Restored? That's a weird line. I don't think it ever lost it since the feature was added in 6.0 (released December 18 2018), it was just annoying to activate.
VirtualBox seems a victim of Oracle's usual apathy as a project custodian. Nearly every other VM vendor has added or accepted (Microsoft employees were even directly involved in PRs to qemu and other) performance improvements on Hyper-V.
It's almost like Oracle is trying to upsell VM servers at the expense of the day-to-day operations of the once well regarded open source project they maintain?~
I’m using hyper-v and virtualbox together, seems to be fine performance-wise. Only reason we’re using vbox is that we already have vagrant scripts set up for it and hyper-v didn’t seem to work as well as a target for vagrant.
Apparently they claim that as of February 19, 2020, they've "Restored the ability to run VMs through Hyper-V, at the expense of performance". https://www.virtualbox.org/wiki/Changelog-6.1