I tried looking into this myself but I couldn’t really find much about this error. The only solutions I could find didn’t work for me. The first one was to use mokutil but at the point where I was supposed to run sudo mokutil -- it gives me the error message “Failed to get file status, MOK.der” even though I did everything it told me to do. The other one was to disable secure boot and then run sudo '/sbin/vboxconfig' but even though it looked like it worked, I’m still getting the error message. I have re-enabled secure boot, so you don’t have to worry about that.
Is there something else I can try or does VirtualBox not work in Linux Mint for some reason?
First of all, check that hardware virtualization is enabled in your UEFI setup.
You need to have packages virtualbox-dkms and linux-headers installed (together with all their dependencies, but you don’t have to check them manually). linux-headers must be of the same version as linux-image. That’s all that you need to get driver properly built. Don’t listen those users who recommend you to remove and reinstall these packages or install additional packages manually, this kind of magic doesn’t work.
Also note that you cannot use kvm and virtualbox simultaneously. If you are using some kvm-based virtualization system, it causes a conflict.