New Google Sites allows HTML embedding

From January 2 you will be able to embed HTML and Javascript into your Google Site.
This was available in the old version of Google Sites but disappeared when the new version was launched.

This was very frustrating if you wanted to embed objects in your website that were not a Google Product such as YouTube. It was impossible to embed features such as a Twitter feed or a 360 degree player creating a site that felt easily customisable, but that has now changed.
Great move Google, making Sites a more flexible platform.

More information available at:

https://gsuiteupdates.googleblog.com/2017/12/embed-html-and-javascript-in-new-google-sites.html