There are several ways to create a link without turning it into an embed:
1. You can highlight some text and then click the link icon in the formatting toolbar that appears (or press Cmd+K or Ctrl+K) to turn that text into a link to any URL.
2. You can type some text before or after a URL in the same paragraph to prevent the URL from being turned into an embed when you press Return.
3. If a link gets turned into an embed and you decide you don't like the embed, you can press Cmd+Z or Ctrl+Z to turn it back into a plain link. (This one currently only works if you're using a device with a physical keyboard.)
Hope this helps!