since xarchiver and squeeze are broken it would be nice to have unp support https://packages.debian.org/en/source/sid/unp
better description and screenshot https://packages.debian.org/en/sid/unp
This archiver doesn't seem to be maintained anymore (correct me if I'm wrong). Currently we support file-roller, ark and now in git master engrampa, isn't that enough? If not, please take a look at: https://git.xfce.org/thunar-plugins/thunar-archive-plugin/tree/scripts You just need to craft a .tap file for your archiver of choice, patches are very welcome :)
Closing since no response was given.