For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:hsk17:science:coot/openSUSE_Tumbleweed/home:hsk17:science:coot.repo
zypper refresh
zypper install coot
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:hsk17:science:coot/15.6/home:hsk17:science:coot.repo
zypper refresh
zypper install coot
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:hsk17:science:coot/15.5/home:hsk17:science:coot.repo
zypper refresh
zypper install coot