For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos:python:applications/openSUSE_Tumbleweed/home:ecsos:python:applications.repo
zypper refresh
zypper install calibre
For openSUSE Slowroll run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos:python:applications/openSUSE_Slowroll/home:ecsos:python:applications.repo
zypper refresh
zypper install calibre
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos:python:applications/15.6/home:ecsos:python:applications.repo
zypper refresh
zypper install calibre