Site keeps redirecting to core/install.php
You've got a problem with your installation. You have two copies of core, as can be seen from the two paths in the error message:

/var/www/html/web/core/includes/bootstrap.inc

/var/www/html/vendor/drupal/core/includes/bootstrap.inc

You should not have a copy of core in your vendor directory. That needs to be removed, though it may also break your site. Make sure to clear the registry drush cr or equivalent after removing that directory.