You need to update your Firefox to at least 115 ESR or perhaps 116.0 as shown in below image as was posted in a couple threads. You appear to be running the old Firefox 106.0.3 on Linux. If you are using a package build installed in your package manager and there are no more updates then perhaps your version of Linux distro is no longer supported with package updates. You either need to update to a currently supported version of your Linux distro or another one or use the Firefox Linux tarballs from Mozilla as they get internal Firefox updates like the macOS and Windows versions. Just make sure wherever you put the tarball version has read/write permissions on the folder for the user to get updates as a easy way is to have folder in Home. https://support.mozilla.org/en-US/kb/install-firefox-linux https://www.firefox.com/download/all/desktop-release/ (Firefox 145.0 Release) https://www.firefox.com/download/all/desktop-esr/ (Firefox 140.5.0esr)

By the way is the WhatsApp web site issue on Firefox on Linux or is it actually on your Android Firefox or Firefox on iPhone?