In the event that you have a site that you don't trust to run through Safe Update in Manage WP, or perhaps a client hasn't entered a service contract yet, you can use this to auto-uncheck updates for them before running updates for your other clients

managewp-site-exclude.js

let excludeSites = [
    'urltoexclude.com',
    'anotherurltoexclude.com',
];

jQuery( '.updates-container .update-row' ).each( function( index, updatesToggle ) {

    if ( ! jQuery( updatesToggle ).hasClass( 'expand' ) ) {
        jQuery( updatesToggle ).click();
    }

    let $updatesGroup = jQuery( updatesToggle ).closest( '.update-group' ),
        $sites = $updatesGroup.find( '.site-url' );

    $sites.each( function( siteIndex, site ) {

        let $checkbox = jQuery( site ).closest( '.site-checkbox-label' ).find( 'mwp-custom-checkbox input[type="checkbox"]' );

        if ( excludeSites.indexOf( jQuery( site ).text().trim() ) > -1 ) {

            // The way that ManageWP's react setup handles state, we have to send a Click event. So we set the checked prop to the opposite of what we want first
            $checkbox.prop( 'checked', true ).click();

        }
        else {

            $checkbox.prop( 'checked', false ).click();

        }

    } );
    
} );