For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:michael-chang:bsc:1226497/openSUSE_Tumbleweed/home:michael-chang:bsc:1226497.repo
zypper refresh
zypper install grub2-x86_64-efi
For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:michael-chang:bsc:1226497/openSUSE_Factory/home:michael-chang:bsc:1226497.repo
zypper refresh
zypper install grub2-x86_64-efi
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:michael-chang:bsc:1226497/15.6/home:michael-chang:bsc:1226497.repo
zypper refresh
zypper install grub2-x86_64-efi