For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:certbot/openSUSE_Tumbleweed/devel:languages:python:certbot.repo
zypper refresh
zypper install certbot-systemd-timer
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:certbot/15.6/devel:languages:python:certbot.repo
zypper refresh
zypper install certbot-systemd-timer
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:python:certbot/15.5/devel:languages:python:certbot.repo
zypper refresh
zypper install certbot-systemd-timer