For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:jloehel/openSUSE_Tumbleweed/home:jloehel.repo
zypper refresh
zypper install java-1_8_0-openjfx
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:jloehel/15.6/home:jloehel.repo
zypper refresh
zypper install java-1_8_0-openjfx
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:jloehel/15.5/home:jloehel.repo
zypper refresh
zypper install java-1_8_0-openjfx