Firefox Esr 78
Is Firefox 78 ESR still 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
Firefox ESR is essentially a more stable and tested version of regular Firefox. This is accomplished by holding back the latest feature upgrades, at least until they've been thoroughly tested in the main branch of Firefox. While foregoing the newest features, ESR still maintains current security and stability patches.
Firefox vs Firefox ESR on Linux - Linux Tutorials - LinuxConfig.org
What is Firefox ESR version?
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. Firefox ESR does not come with the latest features but it has the latest security and stability fixes.
Switch to Firefox Extended Support Release (ESR) for personal use
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