For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ur4ltz:utils/openSUSE_Tumbleweed/home:ur4ltz:utils.repo
zypper refresh
zypper install MultiMarkdown-6
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ur4ltz:utils/15.6/home:ur4ltz:utils.repo
zypper refresh
zypper install MultiMarkdown-6
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ur4ltz:utils/15.5/home:ur4ltz:utils.repo
zypper refresh
zypper install MultiMarkdown-6