In the past, WordPress would just alert you to version updates, but since WP 5x it seems WP will update without even telling you.
As many learned the hard way when WordPress 5.5 was released, WP auto-updated your sites, and many sites ended up broken.
How to prevent this behavior?
Just add this line to the end of your wp-config.php file:
define( 'automatic_updater_disabled', true );
~ Lead Robot