You can use this code to hide events that belong to a specific event category if the user is not logged into the website. Requires EE4

restrict_event_categories.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

add_filter( 'posts_where' , 'my_filter_an_event_category', 11, 2 );

function my_filter_an_event_category( $where, WP_Query $wp_query ) {
         
    if ( 
        !current_user_can('read') &&
        isset( $wp_query->query_vars['post_type'] ) && 
        ( $wp_query->query_vars['post_type'] == 'espresso_events'  || 
        ( is_array( $wp_query->query_vars['post_type'] ) && 
        in_array( 'espresso_events', $wp_query->query_vars['post_type'] ) ) ) && 
        ! $wp_query->is_singular 
    ) 
    {
        global $wpdb;
        //exclude events which have event category id=154
        $filter =  " AND tt.term_id IN ('154')";  
        $where .= " AND $wpdb->posts.ID NOT IN ";  
        $where .= "(SELECT tr.object_id FROM $wpdb->term_relationships AS tr INNER JOIN $wpdb->term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy = 'espresso_event_categories'".$filter.")";  
    }  
    return $where;  
}