How to include jQuery UI in 5.7?
Do you need jQuery UI for logged in users or normal viewing of the web page?
In 5.7, jQuery UI is an asset that is part of concrete5.
You can use your theme page_theme.php to require (or provide) it, so that it is loaded with your pages.
This video covers the topic of using assets.
Here is a list of concrete5 5.7 assets.
This is an example page_theme.php that is part of the Elemental theme.