Can I get a firefox esr release for OS X El Capitan? My MacBookPro3,1 can only run El Capitan!

https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr For the older EOL macOS 10.9, 10.10, 10.11 the most current version to support was the old Firefox 78.15.0esr as in order to use the still being updated older Firefox 115 ESR channel you need macOS 10.12, 10.13, 10.14. https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support Firefox 116.0 and later requires macOS 10.15 (ten.fifteen) at minimum to run. If you need to download Firefox 78.15.0esr then https://archive.mozilla.org/pub/firefox/releases/78.15.0esr/mac/ > clock on a language folder say en-US or en-CA or en-GB then download Firefox 78.15.0esr.dmg Keep in mind that Firefox 78.15.0esr is rather old and vulnerable now and many websites may not work right or even not load now. The old Fx 78.15.0esr is based on the Firefox 78.0 released back on June 30, 2020.