You can combine two measures.

Start by removing Snap package of Firefox by snap remove firefox --purge.

Then follow the steps:

1. prevent Snap installation by purging and pinning it with negative priority:

   
   

   sudo apt-get autopurge snapd
   
   
   
   cat <<EOF | sudo tee /etc/apt/preferences.d/nosnap.pref
   
   # To prevent repository packages from triggering the installation of Snap,
   
   # this file forbids snapd from being installed by APT.
   
   # For more information: https://linuxmint-user-guide.readthedocs.io/en/latest/snap.html
   
   
   
   Package: snapd
   
   Pin: release a=*
   
   Pin-Priority: -10
   
   EOF
   
   

   
   



2. Then install Firefox from

   
   
   
   

   • official repositories as simple as

     
     

     sudo apt-get install firefox
     
     

     
     

     Update april 2022: This option is not anymore applicable in Ubuntu 22.04 and up. Installing the .deb package causes installation of the snap version.

     
     
   
   

   • some third-party (but trusted) repositories

     
     

     a. deb-packaged Firefox from UbuntuZilla - regular or ESR
     
     Add UbuntuZilla repository with its signing key by

     
     

     echo "deb http://downloads.sourceforge.net/project/ubuntuzilla/mozilla/apt all main" | sudo tee -a /etc/apt/sources.list.d/ubuntuzilla.list > /dev/null
     
     sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 2667CA5C
     
     sudo apt-get update
     
     sudo apt-get install firefox-mozilla-build
     
     

     
     

     Note: if one needs ESR version - then replace last command with sudo apt-get install firefox-esr-mozilla-build.

     
     

     Removal is possible by the following commands:

     
     

     sudo rm /etc/apt/sources.list.d/ubuntuzilla.list
     
     sudo apt-get autoremove --purge '*firefox*'
     
     sudo apt-get update
     
     

     
     

     b. deb packaged Firefox ESR version from Mozilla Team PPA

     
     

     To get Firefox ESR version installed from Mozilla Team PPA use commands below:

     
     

     sudo add-apt-repository ppa:mozillateam/ppa
     
     sudo apt-get update
     
     sudo apt-get install firefox-esr
     
     

     
     

     Additional locales may be installed by using packages like firefox-esr-locale-it (example for Italian).

     
     

     To remove deb-packaged Firefox one can use commands like:

     
     

     sudo apt-get install ppa-purge
     
     sudo ppa-purge ppa:mozillateam/ppa
     
     sudo apt-get autoremove --purge
     
     

     
     
   
   

   • Locally extracted Firefox archive

     
     

     If one needs to download and install Firefox to the home folder, then it is possible in the following way:

     
     

     mkdir ~/Software ~/bin
     
     cd ~/Software
     
     wget -c http://ftp.mozilla.org/pub/firefox/releases/93.0/linux-x86_64/en-US/firefox-93.0.tar.bz2
     
     tar -xf firefox-93.0.tar.bz2
     
     ln -sf /home/$USER/Software/firefox/firefox ~/bin/firefox
     
     
     
     # create desktop-file with long command below
     
     mkdir -p ~/.local/share/applications/
     
     cat <<EOF >  ~/.local/share/applications/firefox-user.desktop
     
     #!/usr/bin/env xdg-open
     
     [Desktop Entry]
     
     Encoding=UTF-8
     
     Name=Firefox (local)
     
     GenericName=Browser
     
     Comment=Web Browser
     
     Exec=firefox %u
     
     Icon=/home/$USER/Software/firefox/browser/chrome/icons/default/default48.png
     
     Terminal=false
     
     X-MultipleArgs=false
     
     StartupWMClass=Firefox
     
     Type=Application
     
     Categories=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;
     
     EOF
     
     
     
     update-menus
     
     

     
     

     then logout and login back.

     
     

     To remove such local installation use commands below:

     
     

     rm -rf ~/Software/firefox
     
     rm -v ~/.local/share/applications/firefox-user.desktop
     
     rm -v ~/bin/firefox
     
     update-menus
     
     

     
     
   
   
   
   

Discussion and notes:

My personal choice will be one of deb-based.

I would prefer ESR (2b) to get my Firefox behavior stable as it is needed for enterprise level application.