For standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:dirkmueller:Factory/standard/home:dirkmueller:Factory.repo
zypper refresh
zypper install spack
For p run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:dirkmueller:Factory/p/home:dirkmueller:Factory.repo
zypper refresh
zypper install spack
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:dirkmueller:Factory/15.4/home:dirkmueller:Factory.repo
zypper refresh
zypper install spack