How do you install ProtonVPN on Ubuntu?

To install ProtonVPN on Ubuntu, first, make sure that the system is updated by running `sudo apt update` and `sudo apt upgrade`. Then, download the ProtonVPN Debian package from the official ProtonVPN website. Once downloaded, open the terminal and navigate to the directory containing the .deb file. Install the package using the command `sudo apt install ./protonvpn-stable-release_1.0.1-1_all.deb`, replacing the file name with the exact version you've downloaded. With the repository added, update the package list again using `sudo apt update`. Finally, install ProtonVPN using `sudo apt install protonvpn`. After successful installation, launch ProtonVPN from your applications menu, sign in with your Proton account credentials, and connect to a server as required. Remember to trust sources only from official websites and verify any packages when dealing with VPNs for security integrity.