Use this to disable the wordpress editor for pages and allow only the Beaver Builder page builder.

ultimatum.php

<?php
function disable_gutenberg_4_bb( $can_edit, $post_type ) {

    if($post_type=="page"){
	    $can_edit = false;
        remove_post_type_support( 'page', 'editor' );
        ?>
            <style>.fl-enable-editor, .fl-builder-admin-tabs {display: none !important ;}.fl-builder-admin-ui {display:block !important;}</style>
        <?php
    }

    return $can_edit;

}

add_filter( 'gutenberg_can_edit_post_type', 'disable_gutenberg_4_bb', 10, 2 );
add_filter( 'use_block_editor_for_post_type', 'disable_gutenberg_4_bb', 10, 2 );