There's embedding, and then there's oembedding. The o makes the difference - oembeds generally allow the url or external page to have some kind of tracking done on it, such as tracking how much of a video was watched, or knowing which slide a user is looking at. Embeddding is simply linking to an external page without the possibility of tracking what the user is doing on that page. You can now embed an iframe
Why can't you track an iframe? Because of browser security, tracking, and privacy. When you embed an iframe that links to and shows an external web page or set of pages (perhaps a Microsoft Stream video, or a portal page on your intranet) the course isn't able to track the pages or interactions within that iframe because of how browsers are designed. Good for privacy, bad for courses. When you embed an iframe the page is considered completed as soon as the learner looks at the page.
To embed an iframe, copy the EMBED or IFRAME code from the site you are trying to embed, or use code like:
Then paste this in to the 'Url / Embed' section when adding a new page. The embed will stretch to take up the available space, so you don't have to add any width or height properties yourself.