New Sites has an Embed tool that will attempt to embed content linked to by a simple URL, or for more complex embeddings, HTML Embed code snippets. (NB. Not all embed codes will work due to Google's code restrictions)
On this page are some examples of simple embeds using the Embed > By Url tool
For some websites, when you try to embed the URL for a page the New Sites Embed > By URL tool will attempt to 'intelligently' embed the content of that page into the Sites page. Where it is unable to do this (most websites) it will display a link card.
My hope (and expectation) is that the number of websites that will be supported will increase over time but I could be mistaken.
Some examples below:
Embedded Slideshare page
Again, results in just clickable image link + text