For some time now there are no more official packages for Debian on the ceph.io site. The reason for this is the switch to a C++ version, which was only supported by Debian with Buster. All the more pleasing is the fact that Bernd Zeimetz has been working on the Ceph package for Debian since 28.11.2019 and is currently maintaining it for the current Nautilus versions from 14.2.4-1 for Bullseye and Buster backports.
See changelog of the project: