Install Firefox from Mozilla on Ubuntu 22.04

Download Firefox from Firefox Download Page

tar xjf firefox-*.tar.bz2
mv firefox /opt

Create a symlink to the Firefox executable:

ln -s /opt/firefox/firefox /usr/local/bin/firefox

Create a .desktop file for firefox :

touch ~/.local/share/applications/firefox.desktop
# or
touch /usr/local/share/applications/firefox.desktop

and paste these lines there:

[Desktop Entry]
Version=1.0
Name=Firefox Web Browser
Comment=Browse the World Wide Web
GenericName=Web Browser
Keywords=Internet;WWW;Browser;Web;Explorer
Exec=firefox %u
Terminal=false
X-MultipleArgs=false
Type=Application
Icon=/opt/firefox/browser/chrome/icons/default/default128.png
Categories=GNOME;GTK;Network;WebBrowser;
MimeType=text/html;text/xml;application/xhtml+xml;application/xml;application/rss+xml;application/rdf+xml;image/gif;image/jpeg;image/png;x-scheme-handler/http;x-scheme-handler/https;x-scheme-handler/ftp;x-scheme-handler/chrome;video/webm;application/x-xpinstall;
StartupNotify=true

Logout and login again

References
https://support.mozilla.org/en-US/kb/install-firefox-linux