With which virtualization solution can I boot an Ubuntu install in an USB?
VirtualBox can do it.
It doesnt allow you to directly boot from USB, but it does allow you to attach a physical device to a virtual drive.
So the trick is to create a virtual drive pointing to your USB stick, and then adding that drive to the vistual machine.
Step 1 - Find your USB key ID
Step 2 - Create the Virtual Drive
Step 3 - Add the drive to the virtual machine
More details can be found in this amazing article