Solution:
add_action( 'wp_head', 'change_read_more_to_something' );
function change_read_more_to_something() {
add_filter( 'gettext', 'change_read_more_text');
}
function change_read_more_text( $text ) {
$text = str_ireplace( 'Read More', 'YOUR TEXT', $text );
return $text;
}
Add this code to your functions.php