Bullseye

deb http://deb.debian.org/debian bullseye main contrib non-free
#deb-src http://deb.debian.org/debian bullseye main contrib non-free

deb http://deb.debian.org/debian-security/ bullseye-security main contrib non-free
#deb-src http://deb.debian.org/debian-security/ bullseye-security main contrib non-free

deb http://deb.debian.org/debian bullseye-updates main contrib non-free
#deb-src http://deb.debian.org/debian bullseye-updates main contrib non-free

Buster

deb http://ftp.de.debian.org/debian/ buster main contrib non-free
#deb-src http://ftp.de.debian.org/debian/ buster 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

# buster-updates, previously known as 'volatile'
deb http://ftp.de.debian.org/debian/ buster-updates main contrib non-free
#deb-src http://ftp.de.debian.org/debian/ buster-updates main contrib non-free

Stretch

deb http://ftp.de.debian.org/debian/ stretch main
#deb-src http://ftp.de.debian.org/debian/ stretch main

deb http://security.debian.org/debian-security stretch/updates main
#deb-src http://security.debian.org/debian-security stretch/updates main

# stretch-updates, previously known as 'volatile'
deb http://ftp.de.debian.org/debian/ stretch-updates main
#deb-src http://ftp.de.debian.org/debian/ stretch-updates main