Reference: https://www.tecmint.com/upgrade-debian-10-to-debian-11/

Hacemos upgrade y rebooteamos

apt-get update && apt-get -y upgrade; apt full-upgrade; apt --purge autoremove; systemctl reboot

Modificamos sources.list

cp -v /etc/apt/sources.list /etc/apt/source.list.old

cat  >/etc/apt/sources.list  <<EOF 

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

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

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

EOF

Refrescamos listado de paquetes y rebooteamos

apt update; apt full-upgrade; apt --purge autoremove; systemctl reboot

Se supone que con eso queda pronto. Debería actualizarse NIS, NFS y SLURM y salir todo andando Ojo: mantener los archivos de configuración anteriores!!!