As a workaround, use this Tampermonkey script:
// ==UserScript==
// @name Intl.Segmenter Polyfill for ChatGPT
// @namespace http://tampermonkey.net/
// @version 0.1
// @description Fix missing Intl.Segmenter in Firefox ESR
// @match https://chatgpt.com/*
// @grant none
// ==/UserScript==
(function() {
'use strict';
if (!Intl.Segmenter) {
Intl.Segmenter = function() {
return {
segment: () => [{segment: 'fallback'}]
};
};
}
})();
Get Tampermonkey addon here:
https://addons.mozilla.org/en-US/firefox/addon/tampermonkey/
PS: Thanks ChatGPT for creating that script