For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:maxiotis/15.6/home:maxiotis.repo
zypper refresh
zypper install GASPware
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:maxiotis/15.5/home:maxiotis.repo
zypper refresh
zypper install GASPware
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:maxiotis/15.4/home:maxiotis.repo
zypper refresh
zypper install GASPware