What Does Firefox ESR Mean?
Firefox Extended Support Release - Firefox Extended Support Release (ESR) is an official version of Firefox developed for large organizations like universities and businesses that need to set up and maintain Firefox on a large scale.
How long will Firefox ESR be supported?
Firefox 78 ESR is the last version of Firefox that supports Flash. The last version of that ESR will be 78.15, which is scheduled to be released on 2021-10-05. This means that Flash will officially be out of support on Firefox when Firefox 78 ESR reaches EOL on 2021-11-02.
Firefox | endoflife.date
For end users, it's not necessary to stick with Firefox ESR. Like Mozilla's site says, it's geared towards large organizations. If your distro comes with Firefox ESR by default and it doesn't make much difference to you, then you can leave that version installed.
Firefox vs Firefox ESR on Linux - Linux Tutorials - LinuxConfig ...
Firefox Extended Support Release (ESR), currently based on Firefox 52, is a version of Firefox that comes equipped with the newest security and safety improvements, but uses the older version of Firefox for everything else. This allows users to access tools which are not yet available in Firefox Quantum.
Firefox ESR Installation - Accessibility at Penn State
Firefox 91 ESR includes all of the enhancements since Firefox 78 along with many new features to make your enterprise deployments easier and even more flexible.
Firefox ESR 91.0esr, See All New Features, Updates and Fixes - Mozilla