Bugfix: Show unfiltered results of an ajax/jquery/php page

Hello,
I use this script for product filtering with ajax:
https://www.phpzag.com/product-filter-search-with-ajax-php-mysql/

By default, the page does not show any products in the source code and google does not index them. I fear that this is harmful for SEO and I would like to show all unfiltered results directly when visiting the page, also in the source code. This bugfix must not be done by blackhat techniques like cloaking or hiding content! Maybe the first visit of the page must be synchronous / static, and only if we activate a filter, we use ajax?

You can see a live Demo here:
https://www.phpzag.com/demo/product-search-filter-with-ajax-php-mysql/