* https://askubuntu.com/questions/914997/install-virtualbox-while-keeping-secure-boot
* https://stegard.net/2016/10/virtualbox-secure-boot-ubuntu-fail/
* Assuming you disable secure boot due to a package installation, even when you re-enable secure boot in your system configuration, you may still see [https://askubuntu.com/questions/726052/ubuntu-booting-in-insecure-mode-with-secureboot-enabled
You'll always find a newer version of VirtualBox [https://www.virtualbox.org/wiki/Linux_Downloads using the Oracle ppa], so use that rather than the packaged version that comes with your distro. Warning: if you've already got VirtualBox installed from packages, you should remove it (but not 'completely' meaning don't destroy your existing images). Also, under packaged Ubuntu, you can simply <code>apt-get install virtualbox-guest-additions-iso</code>; however with the PPA, you'll need to download it yourself.
You may need/want to install the "'''Extension Pack'''" for VirtualBox. That's because it provides USB 2.0 and USB 3.0 Host Controller, Host Webcam, VirtualBox RDP, PXE ROM, Disk Encryption, and NVMe. First download the file (it's a tarball with a .vbox-extpack extension), and then use VBoxManage to install it.
<source lang="bash">
VBoxManage extpack listextpacks
VBoxManage extpack --help
VBoxManage extpack install --replace ~/Downloads/Oracle_VM_VirtualBox_Extension_Pack-5.2.13-122773.vbox-extpack
