Move Jetpack menu to bottom of wp-admin

move-jetpack-menu.php

<?php
add_action( 'admin_menu', function() {
	global $menu;

	// Find the Jetpack menu
	$jetpack_menu = false;
	foreach ( $menu as $key => $menu_item ) {
		if ( $menu_item[2] === 'jetpack' ) {
			$jetpack_menu = $menu[$key];
			unset( $menu[$key] ); // Remove it from the current position
			$menu[102] = $jetpack_menu; // Add Jetpack menu to a lower position
			break;
		}
	}

	if ( ! $jetpack_menu ) {
		return;
	}

	ksort( $menu ); // Sort the menu to maintain proper order
}, 999 );

Related: https://gist.github.com/mindctrl/1fc45d251676fa0191cbe1df5373ea25