For SUSE 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:steffens:lvermgeo:server/SUSE_15.4/home:steffens:lvermgeo:server.repo
zypper refresh
zypper install rubygem-json_pure
For SLE 15 SP3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:steffens:lvermgeo:server/SLE_15_SP3/home:steffens:lvermgeo:server.repo
zypper refresh
zypper install rubygem-json_pure
For SLE 15 SP2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:steffens:lvermgeo:server/SLE_15_SP2/home:steffens:lvermgeo:server.repo
zypper refresh
zypper install rubygem-json_pure