The Events Calendar: Filter Bar: If use is not logged in, force them to use a Filter Bar filter in order to see any events in any Events Archive view (e.g. Month, List, Day, etc).

functions.php

<?php

/**
 * The Events Calendar: Filter Bar: If use is not logged in, force them to use
 * a Filter Bar filter in order to see any events in any Events Archive view
 * (e.g. Month, List, Day, etc).
 *
 * @link https://gist.github.com/cliffordp/49d5f296dcae2e6f13773d48d32fd274
 */
add_action( 'tribe_events_pre_get_posts', 'cliff_display_none_unless_filter_bar_in_use' );
function cliff_display_none_unless_filter_bar_in_use( $query ) {
	if ( is_admin() ) {
		return;
	}

	if ( is_user_logged_in() ) {
		return;
	}

	if (
		! class_exists( 'Tribe__Events__Main' )
		|| ! class_exists( 'Tribe__Events__Filterbar__View' )
	) {
		return;
	}

	$archive_slug = Tribe__Events__Main::instance()->rewriteSlug;

	if (
		// if "events" does not match "/events", which is why we start the index at 1
		$archive_slug !== substr( $_SERVER['REQUEST_URI'], 1, strlen( $archive_slug ) )
	) {
		return;
	}

	$probably_using_filter_bar = false;

	// or if no query strings
	if ( ! empty( $_GET ) ) {
		foreach ( $_GET as $key => $value ) {
			if ( substr( $key, 0, strlen( 'tribe_' ) ) ) {
				$probably_using_filter_bar = true;
				break;
			}
		}
	}

	if ( true === $probably_using_filter_bar ) {
		return;
	}

	add_filter( 'posts_where', 'cliff_calendar_appear_empty', 100 );
	add_filter( 'gettext', 'cliff_need_filter_bar_custom_no_events_message', 20, 3 );

}

// throw a wrench in things just to force displaying no results
function cliff_calendar_appear_empty( $where ) {
	return $where . ' AND 1=0 ';
}

// adapted from https://theeventscalendar.com/knowledgebase/change-the-wording-of-any-bit-of-text-or-string/
function cliff_need_filter_bar_custom_no_events_message( $translation, $text, $domain ) {

	$custom_text = array(
		'There were no results found.' => 'Please choose a filter in order to display events.',
	);

	if (
		0 === strpos( $domain, 'the-events-calendar' )
		&& array_key_exists( $translation, $custom_text )
	) {
		$translation = $custom_text[ $translation ];
	}

	return $translation;
}