How do I disable the changing of the permalink for published posts (for non-admin)?

You could do something like the following, this should go in your Child Theme’s functions.php or if not using a Child Theme then add to a custom plugin:

    function hide_permalink_metabox( $is_post_edit_page ) {
    if ( !current_user_can('update_core') ) {  // allows Admins to edit the permalink
    echo '<style>
    div#edit-slug-box {display:none!important;}
    </style>';
}

You may need to double-check the actual ID of the permalink DIV, it might be different from mine depending on what version of WP you’re using and if you’re using the Blocks Editor (I don’t, I use the Classic Editor).