$ cat /etc/apt/sources.list
deb http://deb.debian.org/debian buster main contrib non-free
#deb-src http://deb.debian.org/debian buster main contrib non-free
deb http://deb.debian.org/debian buster-updates main contrib non-free
#deb-src http://deb.debian.org/debian buster-updates main contrib non-free
deb http://deb.debian.org/debian buster-backports main contrib non-free
#deb-src http://deb.debian.org/debian buster-backports main contrib non-free
deb http://security.debian.org/ buster/updates main contrib non-free
#deb-src http://security.debian.org/ buster/updates main contrib non-free
$ cat /etc/apt/sources.list.d/armbian.list
deb http://apt.armbian.com buster main buster-utils buster-desktop