Hi, I was also unpleasently surprised that rsnapshot is not in Bullseye and there's no mention of it in the release notes either. I don't how the process or rules in Debian are for such a case, but please find a way to either reintroduce rsnapshot into the stable distribution or at least provide a bullseye-backports package for it. It's simply a useful and mature piece of software.
Regards, Timo