Firefox from .deb

Since this version of Ubuntu, firefox will be installed as a snap instead of a .deb. Even the sudo apt install firefox installs a package that installs the snap version. Like chromium in Ubuntu 20.04 does.

Step 1: Remove the Firefox Snap by running the following command in a new Terminal window:

sudo snap remove firefox

Step 2: Add the (Ubuntu) Mozilla team PPA to your list of software sources:

sudo add-apt-repository ppa:mozillateam/ppa

Step 3: Next, alter the Firefox package priority to ensure the PPA/deb/apt version of Firefox is preferred. This can be done using a slither of code from FosTips (copy and paste it whole, not line by line):

echo '

Package: *

Pin: release o=LP-PPA-mozillateam

Pin-Priority: 1001

' | sudo tee /etc/apt/preferences.d/mozilla-firefox

Step 4: Since you’ll (hopefully) want future Firefox upgrades to be installed automatically, Balint Reczey shares a concise command on his blog that ensures it happens:

echo 'Unattended-Upgrade::Allowed-Origins:: "LP-PPA-mozillateam:${distro_codename}";' | sudo tee /etc/apt/apt.conf.d/51unattended-upgrades-firefox

Step 5: Finally, install Firefox via apt by running this command:

sudo apt install firefox

As soon as the Firefox installation completes pop open the app launcher and click on the Firefox icon to launch a de-Snapped version you can pin to the Ubuntu dock.

To install GNOME extentions, just install: sudo apt install gnome-shell-extension-manager

This works for the snap version as well.