For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:fbonazzi/openSUSE_Tumbleweed/home:fbonazzi.repo
zypper refresh
zypper install sway-xkb-layout-generator
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:fbonazzi/15.6/home:fbonazzi.repo
zypper refresh
zypper install sway-xkb-layout-generator
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:fbonazzi/15.5/home:fbonazzi.repo
zypper refresh
zypper install sway-xkb-layout-generator