firefox-esr from mozilla:legacy project
Select Your Operating System
Add repository and install manually
For openSUSE Leap 42.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/mozilla:legacy/openSUSE_Leap_42.3/mozilla:legacy.repo zypper refresh zypper install firefox-esr
For openSUSE Leap 15.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/mozilla:legacy/openSUSE_Leap_15.0/mozilla:legacy.repo zypper refresh zypper install firefox-esr