You can try Judge.me Product Reviews. We are preparing to launch Judge.me on Squarespace very soon and looking for some early users to try out the extension.
Read this article for this installation guide: https://support.judge.me/en/support/solutions/articles/44002266545-how-to-install-judge-me-review-widgets-on-squarespace
Installation can be done without any coding and you can contact support@judge.me if you need any help.