Для openSUSE Tumbleweed запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:darix:apps/openSUSE_Tumbleweed/home:darix:apps.repo
zypper refresh
zypper install rubygem-json-jwt
Для 15.5 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:darix:apps/15.5/home:darix:apps.repo
zypper refresh
zypper install rubygem-json-jwt
Для 15.4 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:darix:apps/15.4/home:darix:apps.repo
zypper refresh
zypper install rubygem-json-jwt