Para openSUSE Factory execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/Archiving/openSUSE_Factory/Archiving.repo
zypper refresh
zypper install stuffit
Para 15.6 execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/Archiving/15.6/Archiving.repo
zypper refresh
zypper install stuffit
Para 15.5 execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/Archiving/15.5/Archiving.repo
zypper refresh
zypper install stuffit