For openSUSE Factory PowerPC run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:michael-chang:devel:grub:appendedsig-2.11/openSUSE_Factory_PowerPC/home:michael-chang:devel:grub:appendedsig-2.11.repo
zypper refresh
zypper install grub2
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:michael-chang:devel:grub:appendedsig-2.11/15.4/home:michael-chang:devel:grub:appendedsig-2.11.repo
zypper refresh
zypper install grub2
For 15.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:michael-chang:devel:grub:appendedsig-2.11/15.3/home:michael-chang:devel:grub:appendedsig-2.11.repo
zypper refresh
zypper install grub2