Para openSUSE Tumbleweed execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:schaats/openSUSE_Tumbleweed/home:schaats.repo
zypper refresh
zypper install firefox-esr
Para openSUSE Slowroll execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:schaats/openSUSE_Slowroll/home:schaats.repo
zypper refresh
zypper install firefox-esr
Para 15.6 execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:schaats/15.6/home:schaats.repo
zypper refresh
zypper install firefox-esr