Works on every platform, because it is one script tag. You connect the places your reviews already are, choose a layout, and paste the code wherever the reviews should appear. It updates itself afterwards.
Platform-specific instructions: Shopify, WordPress, Wix, Squarespace, WooCommerce and the rest.
WooCommerce, Magento, BigCommerce and Squarespace Commerce all have product reviews built in, and they are fine for reviews left on your own store. What none of them can do is show a review someone left on Google or a marketplace.
Option three: hardcode them
Paste the text into your page as ordinary content. No dependency, no cost, and you maintain it by hand forever. Reasonable for three testimonials that will not change; unreasonable for anything that should stay current.