Installing vagrant environment on MacOs Big Sur is a real pain…a nightmare and possibly is a much harder task than completing the course itself
It required some Unix/Linux knowlegde, VBox experience and a couple of hints However I have found a way to have the setup running.
You have to take care of installing some kernel modules together with VBoxAdditional iso image and some tweak in mouting the shared folder.
Also be aware that VBox 6.0.x does not work well in Big Sur (at least in my installation)
If someone needs help please ask I might have some suggestion !