Told to use Firefox 115 ESR on old Mac OS but just noticed I'm on version 140, without ESR???

Is this with a different Mac desktop/laptop as you appear to be posting with Firefox 115 ESR on macOS 10.13 according to the UaserAgent you used to post this thread. Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:109.0) Gecko/20100101 Firefox/115.0 Firefox 116.0 and later including the current Firefox 140 ESR requires macOS 10.15 (ten.fifteen) or later to run. If you are downloading from https://www.firefox.com/download/all/desktop-esr/osx/ make sure you select [Download ESR 115] to download the current Fx 115.36.0esr as the [Download now] will serve you the current Fx 140.0 ESR. https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support