Firefox Esr 91
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
Is Firefox ESR no longer supported?
Firefox ESR versions are maintained for a longer period compared to stable releases. ... The latter will see two additional releases, Firefox 78.14 ESR and Firefox 78.15 ESR before it will be discontinued; this will happen in October 2021. Firefox 91 ESR marks the beginning of a new base for extended support releases.
Firefox ESR 91: new ESR version will be released tomorrow - gHacks
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.
Switch to Firefox Extended Support Release (ESR) for personal use
What is the latest Firefox ESR version?
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.
Firefox | endoflife.date