Here is a simple snippet by @pbosakov that needs to be placed in function.php file in order to move all your events online due to COVID-19.

function.php

/* all events moved online due to COVID-19 */
if (!function_exists('custom_event_schema_extras')) {
  function custom_event_schema_extras($_data, $args, $event) {
    $_data->eventStatus = 'EventMovedOnline';
    $_data->eventAttendanceMode = 'OnlineEventAttendanceMode';
    return $_data;
  }
  add_filter('tribe_json_ld_event_object', 'custom_event_schema_extras', 10, 3);
}