jQuery doesn’t work

Hey there. I’m running WP 5.7

I’m trying to develop an application inside WordPress using jQuery and jQuery UI, so for this I’m using a child theme.

So I tried to add jQuery code everywhere: footer.php, header.php, functions.php with all the reccomendations I read in the internet: noConflict mode; wp_enqueue_script but it just doesn’t execute at all. Firebug doesn’t show any error.

Even basic code don’t work

jQuery(document).ready(function(){
		alert('test');
	});

Thank you in advance!