Today I needed a specific _really_ old #Firefox ESR version (don’t ask, answer may be unsettling) and look, stuff is all still on the Mozilla attic: https://ftp.mozilla.org/pub/firefox/releases/45.0esr/linux-x86_64. Neat! Somewhat dusty but it still starts flawless (on a tmp profile, of course) 🙋 (https://beko.famkos.net/t/1SpY)