FWIW, it works fine on Arch Linux, and it really should be as simple as having the calibre binary plugins properly compiled (it has nothing whatsoever to do with any icu python modules).
IOW, this is entirely Debian's responsibility, and we have no idea what they may have messed up.
But as darryl said, if the distro cannot get it working properly, just use the binary installer.
And the distros usually manage to mess up
something regarding calibre. Usually the deliberately-removed python modules which are replaced by incompatible upstream projects.