Show in Rest API?

Well, I used the following and it worked to get the event post types and categories to show in Generate Blocks query loop:

/*add rest API support to event post type*/
add_filter( 'register_post_type_args', 'my_post_type_args', 10, 2 );

function my_post_type_args( $args, $post_type ) {

    if ( 'event' === $post_type ) {
        $args['show_in_rest'] = true;

        // Optionally customize the rest_base or rest_controller_class
        $args['rest_base']             = 'events';
        $args['rest_controller_class'] = 'WP_REST_Posts_Controller';
    }

    return $args;
}
/**
 * Add REST API support to an already registered taxonomy event category and tags.
 */
add_filter( 'register_taxonomy_args', 'my_taxonomy_args', 10, 2 );

function my_taxonomy_args( $args, $taxonomy_name ) {

    if ( 'event-categories' === $taxonomy_name ) {
        $args['show_in_rest'] = true;

        // Optionally customize the rest_base or rest_controller_class
        $args['rest_base']             = 'event-categories';
        $args['rest_controller_class'] = 'WP_REST_Terms_Controller';
    }

    return $args;
}

Now I need to figure out how to add event tags to that without causing an error:)

The block editor (Rest API) can be enabled for event, recurring-event and location post types by setting the EM_GUTENBERG constant to true.

define( 'EM_GUTENBERG', true );

This doesn’t appear to enable for event-tags or event-categories taxonomies.

The plugin provides filter hooks for event taxonomies.

apply_filters( 'em_ct_tags', array $args );

apply_filters( 'em_ct_categories', array $args );

Usage

if ( defined( 'EM_GUTENBERG' ) && EM_GUTENBERG ) {
	add_filter( 'em_ct_tags', 'enable_block_editor' );
	add_filter( 'em_ct_categories', 'enable_block_editor' );
}

/**
 * Enable Rest API for Event Taxonomies
 *
 * @param array $args
 * @return  array $args modified array
 */
function enable_block_editor( $args ) {
	$args['show_in_rest'] = true;
	return $args;
}