I just figured it out after some research and trial.

Here's how I fixed it:

I simply closed that terminal and opened a new one, and ran the command again:

minikube start

OR

minikube start --driver=virtualbox

And it worked fine.

Note: By default minikube attempts to use Docker as the driver, but you specify VirtualBox as your preferred driver, which has some advantages.

Another way would have been to reload the Ubuntu bash terminal:

bash --login

Note:

If all the above techniques do not work, you add the Minikube executable to your path:

sudo mv minikube /usr/local/bin

You can then verify the Minikube executable path:

which minikube.

That's all.

I hope this helps