Update Debian 11 (Bullseye) to Debian 12 (Bookworm)

Prepare:

apt update
apt upgrade -qqy
apt dist-upgrade -qqy

Update APT:

sed -i 's/bullseye/bookworm/g' /etc/apt/sources.list

Upgrade:

apt update && \
apt upgrade -qqy --without-new-pkgs && \
apt full-upgrade -qqy && \
apt --purge autoremove -qqy

Reboot:

reboot