[jandrese]

If you install to the HDD and don't use any binary drivers it works fine. If you're trying to boot from USB you usually have to disable SecureBoot in the BIOS.

I usually disable SecureBoot when I install a machine. The extra protections aren't worth losing the ability to run VirtualBox.

[zamadatix]

As of some time last year VB on Ubuntu now signs its modules automatically FWIW.