For openSUSE Leap 15.2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:aspiers/openSUSE_Leap_15.2/home:aspiers.repo
zypper refresh
zypper install shellinabox
For openSUSE Leap 15.1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:aspiers/openSUSE_Leap_15.1/home:aspiers.repo
zypper refresh
zypper install shellinabox
For openSUSE Leap 15.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:aspiers/openSUSE_Leap_15.0/home:aspiers.repo
zypper refresh
zypper install shellinabox