Note : Make sure you watch the video below, to install firefox without any problems!
About Firefox
Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation.
It uses the Gecko rendering engine to display web pages, which implements current and anticipated web standards. Wikipedia
Method 1
Make Sure Your System Is UpTo Date:
sudo apt update -y && sudo apt upgrade -y
Adding The Repository Key:
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys A6DCF7707EBC211F
sudo apt-add-repository "deb http://ppa.launchpad.net/ubuntu-mozilla-security/ppa/ubuntu focal main"
sudo apt install firefox
Method 2
Make Sure Your System Is UpTo Date:
sudo apt update -y && sudo apt upgrade -y
Installation of essential dependencies:
sudo apt install snapd && sudo snap install core
Refreshing Snapd Installation:
sudo systemctl restart snapd
Installing Snap Documentation: https://snapcraft.io/docs/installing-snapd
sudo snap install firefox
Method 3
Make Sure Your System Is UpTo Date:
sudo apt update -y && sudo apt upgrade -y
Adding the official Flatpak PPA:
sudo add-apt-repository ppa:flatpak/stable
Installation of flatpak:
sudo apt install flatpak
Installing flatpak plugin:
sudo apt install gnome-software-plugin-flatpak
Add the Flathub repository:
flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
Installing Firefox:
flatpak install flathub org.mozilla.firefox