It's definitely possible for Debian to package unofficial releases out of the upstream VCS. You can sometimes tell that's what happened because it'll have somet

It's definitely possible for Debian to package unofficial releases out of the upstream VCS. You can sometimes tell that's what happened because it'll have something like ~git20191005.f8ab33 in the Debian package's version number. In this particular case, the Debian maintainer seems to prefer to wait for upstream to release an official Python3-supporting version of Calibre though: https://github.com/norbusan/calibre-debian/blob/master/debian/NEWS https://github.com/norbusan/calibre-debian/blob/master/debia... It's basically up to the maintainer either way. The freeze for the next Debian release is at least months away (no date set yet), so it's not too urgent, and waiting for upstream is still reasonable at this point.