Для 15.6 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:backports/15.6/devel:languages:python:backports.repo
zypper refresh
zypper install python-proton-vpn-killswitch-network-manager
Для 15.5 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:backports/15.5/devel:languages:python:backports.repo
zypper refresh
zypper install python-proton-vpn-killswitch-network-manager
Для 15.4 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:backports/15.4/devel:languages:python:backports.repo
zypper refresh
zypper install python-proton-vpn-killswitch-network-manager