For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:fschuett/openSUSE_Tumbleweed/home:fschuett.repo
zypper refresh
zypper install rxtx-java
For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:fschuett/openSUSE_Factory/home:fschuett.repo
zypper refresh
zypper install rxtx-java
For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:fschuett/16.0/home:fschuett.repo
zypper refresh
zypper install rxtx-java
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:fschuett/15.6/home:fschuett.repo
zypper refresh
zypper install rxtx-java