firefox-esr from home:dliw:mozilla project
Select Your Operating System
Add repository and install manually
For openSUSE Leap 15.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:dliw:mozilla/openSUSE_Leap_15.3/home:dliw:mozilla.repo zypper refresh zypper install firefox-esr