Virtualbox : Kernel driver not installed (rc=-1908) error solved in Ubuntu 20.4

sudo apt-get update

sudo apt-get upgrade

sudo apt-get install mokutil

openssl req -new -x509 -newkey rsa:2048 -keyout MOK.priv -outform DER -out MOK.der -nodes -days 36500 -subj "/CN=VirtualBox/"

sudo mokutil --import MOK.der

sudo reboot

Enroll MOK > Continue > and it will ask you for the password

sudo modprobe vboxdrv