Prevent/Disable Automatic Update Check

WordPress automatically checks for updates to itself and all installed themes and plugins. This adds an annoyingly long delay to loading (any) WordPress pages. In only happens once per day and subsequent page-loads don’t do it, but it is so long, that it makes me think twice about whether it is worth opening that first page at all (especially if I only need to do a quick thing rather than spending all day in WordPress).

I only update once in a while anyway, and would much rather perform updates manually anyway, so I created a plugin to remove the Updates button from the admin bar. I thought that would do the trick, but apparently in only removes the button and the actual check is still performed in the background.

Every other program in the world lets you turn them off automatic updates, so I expect that there should be a way to do the same for WordPress, but if there is, it is a little too-well—hidden.

When I tried to find a solution, all of the questions that came up were the opposite, about finding a way to force automatic updates to actually apply (not just automatically check for updates).

How can automatic update checks be turned off in WordPress?

How to disable core auto updates but enable plugins and themes auto
updates

If you want to stop the autoupdates of the WordPress core, but to
enable them for your Plugins and/or Themes, you can add these lines in
the wp-config.php file: Stop the core auto updates:

define( 'WP_AUTO_UPDATE_CORE', false );

Then Enable the plugins/themes:

add_filter( 'auto_update_plugin', '__return_true' );
add_filter( 'auto_update_theme', '__return_true' );

How to completely disable the WordPress auto updates

If you want to disable the WordPress auto updates completely, open the
wp-config.php file and add this line to it:

define( 'AUTOMATIC_UPDATER_DISABLED', true );