For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:mnhauke:games/openSUSE_Tumbleweed/home:mnhauke:games.repo
zypper refresh
zypper install snes9x
For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:mnhauke:games/16.0/home:mnhauke:games.repo
zypper refresh
zypper install snes9x
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:mnhauke:games/15.6/home:mnhauke:games.repo
zypper refresh
zypper install snes9x