Comment 6 for bug 1899288

Same issue: after upgrading from Ubuntu 20.04 to 20.10 my Virtualbox installation was missing (removed as part of the upgrade). Attempts to re-install indicated a conflict between the python pre-req and dh-python. I performed the following and all appears to be working now:

sudo apt remove dh-python
sudo apt install ./virtualbox-6.1_6.1.16-140961~Ubuntu~eoan_amd64.deb
sudo apt-get update
sudo apt-get upgrade