For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:agraul:salt-test-dev/15.5/home:agraul:salt-test-dev.repo
zypper refresh
zypper install salt-master
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:agraul:salt-test-dev/15.4/home:agraul:salt-test-dev.repo
zypper refresh
zypper install salt-master
For 15.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:agraul:salt-test-dev/15.3/home:agraul:salt-test-dev.repo
zypper refresh
zypper install salt-master