Go to this website and download the linux version of Tor Browser. Change the permission of the file to run as the executable file.
Once the file is executable, open a terminal in that location. Now, enter the command below to register the Tor browser as a desktop app.
cd tor-browser-linux-x86_64-13.5.3/tor-browser
./start-tor-browser.desktop --register-app
You will find that Tor Browser as a default application.