For standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:-miska-:gpg/standard/home:-miska-:gpg.repo
zypper refresh
zypper install gpg2
For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:-miska-:gpg/openSUSE_Factory/home:-miska-:gpg.repo
zypper refresh
zypper install gpg2
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:-miska-:gpg/15.5/home:-miska-:gpg.repo
zypper refresh
zypper install gpg2
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:-miska-:gpg/15.4/home:-miska-:gpg.repo
zypper refresh
zypper install gpg2