For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:mailman/openSUSE_Tumbleweed/devel:languages:python:mailman.repo
zypper refresh
zypper install python-mailmanclient
For openSUSE Factory zSystems run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:mailman/openSUSE_Factory_zSystems/devel:languages:python:mailman.repo
zypper refresh
zypper install python-mailmanclient
For openSUSE Factory PowerPC run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:mailman/openSUSE_Factory_PowerPC/devel:languages:python:mailman.repo
zypper refresh
zypper install python-mailmanclient
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:mailman/15.6/devel:languages:python:mailman.repo
zypper refresh
zypper install python-mailmanclient
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:mailman/15.5/devel:languages:python:mailman.repo
zypper refresh
zypper install python-mailmanclient