For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Application:ERP:GNUHealth:4.0/openSUSE_Tumbleweed/Application:ERP:GNUHealth:4.0.repo
zypper refresh
zypper install proteus
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Application:ERP:GNUHealth:4.0/15.4/Application:ERP:GNUHealth:4.0.repo
zypper refresh
zypper install proteus
For 15.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Application:ERP:GNUHealth:4.0/15.3/Application:ERP:GNUHealth:4.0.repo
zypper refresh
zypper install proteus