If you don’t want to use shortcodes, then the only other option you have is to use the render_query method, like what was discussed on that other thread you mentioned. Try using the same code which I’ve pasted below. Just make sure to change the page_id to the correct one.
// Add global footer to footer
function global_footer(){
FLBuilder::render_query( array(
'page_id' => 123
));
};
add_action('fl_before_footer', 'global_footer');
Just to answer your questions above, the code I gave goes to your theme’s(preferably child theme) functions.php file. What it does is it calls the contents of the page with ID 123, and add it to the fl_before_footer action, which fires before the opening footer </div> tag.