For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:dheidler:nheko/openSUSE_Tumbleweed/home:dheidler:nheko.repo
zypper refresh
zypper install mpark-variant
For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:dheidler:nheko/16.0/home:dheidler:nheko.repo
zypper refresh
zypper install mpark-variant
For 15.7 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:dheidler:nheko/15.7/home:dheidler:nheko.repo
zypper refresh
zypper install mpark-variant
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:dheidler:nheko/15.6/home:dheidler:nheko.repo
zypper refresh
zypper install mpark-variant