For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:s_liehmann:nss-pam-ldapd/15.6/home:s_liehmann:nss-pam-ldapd.repo
zypper refresh
zypper install nss-pam-ldapd
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:s_liehmann:nss-pam-ldapd/15.5/home:s_liehmann:nss-pam-ldapd.repo
zypper refresh
zypper install nss-pam-ldapd
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:s_liehmann:nss-pam-ldapd/15.4/home:s_liehmann:nss-pam-ldapd.repo
zypper refresh
zypper install nss-pam-ldapd