primeiro - apt update && apt upgrade && apt dist-upgrade && apt autoremove && apt autoclean && find /etc -name '.dpkg-' -o -name '.ucf-' -o -name '*.merge-error' && reboot
segundo - mkdir ~/apt && cp /etc/apt/sources.list ~/apt && cp -rv /etc/apt/sources.list.d/ ~/apt && sed -i 's/buster\/updates/bullseye-security/g;s/buster/bullseye/g' /etc/apt/sources.list && sed -i 's/buster\/updates/bullseye-security/g;s/buster/bullseye/g' /etc/apt/sources.list.d/* && apt update && apt upgrade --without-new-pkgs
terceiro - apt full-upgrade && apt autoremove && apt autoclean && reboot
https://ostechnix.com/upgrade-to-debian-11-bullseye-from-debian-10-bust…
https://pve.proxmox.com/wiki/Upgrade_from_6.x_to_7.0
Chapter 5. Issues to be aware of for bullseye - https://www.debian.org/releases/bullseye/amd64/release-notes/ch-informa…