Sounds like you were trying to install the desktop Firefox version for Windows or macOS. https://support.mozilla.org/en-US/kb/run-firefox-chromeos https://www.mozilla.org/firefox/browsers/chromebook/ https://www.techradar.com/how-to/how-to-install-firefox-on-a-chromebook https://techpp.com/2021/12/02/install-firefox-on-chromebook/ Depending on what CPU and ChromeOS version it has, you may have a few different options. btw the Firefox for iOS section you posted this in originally is for Firefox on iPhone/iPad.