Comment 1 for bug 1736116

LocutusOfBorg (costamagnagianfranco) wrote in https://bugs.launchpad.net/ubuntu/+source/virtualbox/+bug/1729568/comments/21 :

@geryon, can you please try what Vlad mentioned here?

"Boot issue solved by removing intel-microcode package - no idea why it was installed."

I think you just need to disable iommu, but removing that package might be even better, or trying the one from bionic might also help us
https://launchpad.net/ubuntu/+source/intel-microcode