To uninstall Firefox from Ubuntu and then install it using the apt package manager, you can follow these steps:
Uninstall Firefox
1. Open a terminal by pressing `Ctrl + Alt + T` or by searching for `Terminal` in the application launcher.
2. To uninstall Firefox, you can use the apt command with the remove option. You can choose to keep your configuration files (bookmarks, settings, etc.) or remove them along with Firefox. To keep the configuration files, use [1][2][5]:

    sudo apt remove firefox

If you want to remove the configuration files as well, use:

    sudo apt purge firefox

3. Confirm the uninstallation by typing `y` when prompted and press Enter.

Install Firefox:
1. To install Firefox using apt, you can use the following command:

    sudo apt install firefox

2. The apt package manager will download and install the latest version of Firefox from the Ubuntu repository. Follow the prompts to complete the installation.
3. Once the installation is complete, you can open Firefox by searching for it in the application launcher or running the following command:

    firefox

It is worth noting that starting from Ubuntu 21.10, Firefox comes installed as a snap package instead of the traditional DEB package. To uninstall Firefox in this case, you can use the command `sudo snap remove firefox`. To install Firefox from the apt package, you can use the command `sudo apt install firefox` [3][5].
By following the above steps you can successfully uninstall Firefox and then reinstall it using the apt package manager on your Ubuntu system.

Uninstall Firefox:
1. Uninstall Firefox: The `sudo apt remove firefox` command removes the Firefox package but retains configuration files.
* sudo is used to run the command as the superuser (administrator) because uninstalling software typically requires elevated privileges.
* apt is the package manager.
* remove is the command to uninstall a package.
* firefox is the name of the package to be removed.
The remove command will remove the Firefox package but will keep the configuration files. This is useful if you plan to reinstall Firefox later and want to preserve your settings and bookmarks.
2. Purge Firefox: The `sudo apt purge firefox` command not only removes the Firefox package but also deletes its configuration files.
* purge is the command to remove a package and its configuration files. Use this command if you want to completely remove Firefox and all associated settings.
3. Autoremove: The `sudo apt autoremove` command is used to remove any residual packages or dependencies that were automatically installed but are no longer needed. This helps to free up disk space

Install Firefox from apt (Recommended Method):
1. Update Package List: Before installing any software, it is a good practice to update the package list to ensure you have the latest information about available packages. The command sudo apt update fetches the latest package information from the repositories.
2. Install Firefox: The sudo apt install firefox command installs Firefox from the official Ubuntu repositories. It resolves dependencies and installs the software.
3. Verify Firefox Installation: After installation, you can use the firefox --version command to verify that Firefox is installed. It will display the installed Firefox version.

Why Use apt for Firefox Installation:
Using apt to install Firefox has several advantages:
1. Official Repository: apt installs software from the official Ubuntu repositories, ensuring that you get a stable and tested version of Firefox.
2. Updates: Firefox installed via apt will receive updates and security patches through the system's package manager, making it easy to keep your browser up to date.
3. Dependency Resolution: apt automatically resolves and installs any dependencies required by Firefox, simplifying the installation process.
4. System Integration: Firefox installed via apt integrates smoothly with your Ubuntu system, including menu entries and file associations.