Just a couple notes from the article:
You cannot set a bootloader password for AWS or other cloud services
Apt Armor is specific to Ubuntu / Debian. SELinux is used on RHEL / CentOS / Fedora
AppArmor is default on SUSE as well. And you can run SELinux on Debian / Ubuntu if you want.
BTW, AppArmor just replaced SELinux as default on Debian 10. So that was only a couple of months ago.