how to install or update firefox

You appear to be using a old Ubuntu package build of Firefox 88.0 (released back on April 19, 2021) Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:88.0) Gecko/20100101 Firefox/88.0 If you are not able to get Firefox package updates in your package manager then your version of Linux distro is likely End of Life or EOL in software package updates. To use the current versions of Firefox you will either have to update to a current support version of Linux distro or you could use the Firefox Linux tarball from Mozilla. However if your PC is rather old with a 32-bit CPU then 32-bit Linux support was dropped as of Firefox 145.0 and later so it would be best to use Firefox 140 ESR. I mention this because the UserAgent or UA no longer shows if you are using 32-bit and shows you have 64-bit Firefox even on a 32-bit system. https://support.mozilla.org/en-US/kb/firefox-has-ended-support-32-bit-linux https://support.mozilla.org/en-US/kb/install-firefox-linux