For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ellessar/openSUSE_Tumbleweed/home:ellessar.repo
zypper refresh
zypper install libgmpxx4
For openSUSE Slowroll run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ellessar/openSUSE_Slowroll/home:ellessar.repo
zypper refresh
zypper install libgmpxx4
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ellessar/15.6/home:ellessar.repo
zypper refresh
zypper install libgmpxx4
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ellessar/15.5/home:ellessar.repo
zypper refresh
zypper install libgmpxx4