For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:andythe_great:branches:games:tools/openSUSE_Tumbleweed/home:andythe_great:branches:games:tools.repo
zypper refresh
zypper install goverlay
For openSUSE Leap 15.2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:andythe_great:branches:games:tools/openSUSE_Leap_15.2/home:andythe_great:branches:games:tools.repo
zypper refresh
zypper install goverlay