Comment 4 for bug 857824

an update to a new version can only be done via backports.
do people often need 2.32 and 2.4 at the same time? that would require renaming the unison package to add a version and make it coinstallable
a simple backport of unison would be simpler but people would have to deinstall and reinstall to change version

see https://help.ubuntu.com/community/UbuntuBackports
use the requestbackport script from ubuntu-dev tools to request one.