rpress_is_ajax_enabled

This filter is applied to use checks whether AJAX is enabled, it is returned bool true when RPRESS AJAX is enabled (for the cart), false otherwise, it includes one parameter.
$retval -> store a function.

An example of how you can append is below:
function is_ajax_enabled( false = '' ) {
$ajax = // check the ajax function is enabled;
}
add_filter('rpress_is_ajax_enabled', 'is_ajax_enabled');