https://www.cnet.com/news/super-bowl-2019-how-to-watch-patriots-rams-online-start-time-and-much-more/

You can livestream Super Bowl LIII on CBSSports.com or the CBS Sports app for free -- no authentication is required. You can also watch on CBS All Access if you live in one of the 200 markets where the service offers live TV. CBS All Access costs $5.99 a month, or $9.99 a month with no commercials. 

If you're willing to watch on a phone or tablet and not screencast to your TV, you can livestream the Super Bowl with the NFL Mobile app or the Yahoo Sports app for free.