According to
https://wiki.debian.org/NewInBullseye
However, it seems that in the new Debian rootfs (bullseye with kernel 5.13.6) it is still using the previous format...
https://wiki.debian.org/NewInBullseye
Quote
The format of the /etc/apt/sources.list line for the security repository has changed. It should look something like this:
deb https://security.debian.org/debian-security bullseye-security main
However, it seems that in the new Debian rootfs (bullseye with kernel 5.13.6) it is still using the previous format...