For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/openSUSE:infrastructure:wiki/openSUSE_Tumbleweed/openSUSE:infrastructure:wiki.repo
zypper refresh
zypper install mediawiki_1_27-openSUSE
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/openSUSE:infrastructure:wiki/15.6/openSUSE:infrastructure:wiki.repo
zypper refresh
zypper install mediawiki_1_27-openSUSE
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/openSUSE:infrastructure:wiki/15.5/openSUSE:infrastructure:wiki.repo
zypper refresh
zypper install mediawiki_1_27-openSUSE