I see an option for MySql and Postgres, and have read help messages for sqlite, but I don't see anyway to use it or to install it.  So it appears that it's available or else there wouldn't be any help messages, but I can't find it.  I can't do any 'sudo', so no 'apt install', so don't know how to invoke and use it!
sqlite is already installed. You don't need to invoke anything to install it. Just configure your web app to use it.
pythonanwhere newbie: I don't see sqlite option