By default, the Beaver Builder Theme footer shows a single centered column with the copyright symbol and year, your site title, and the text "Powered by Beaver Builder" with a link:
This default text appears in the one-column layout at Customize > Footer > Footer Layout after you first install the Beaver Builder Theme, but even if you delete it there, it will still appear on your site. That's because this footer content actually comes from the file your-site/wp-content/themes/bb-theme/includes/copyright.php.
There's an easy way to change this default footer text without touching the copyright.php file. On the Customizer > Footer > Footer Layout tab, you can either configure your own footer layout and content or choose None for the Layout option to remove the footer entirely. See the article about how to customize footer layout in the Customizer.