The iframe tag itself is not supported within the rich text formula field, but there's a workaround.
1. Create a URL field (or URL Formula - whatever you prefer) and enter the URL that should go in the src property of the iframe tag. Remember to use an embeddable URL where applicable (YouTube, etc.).
2. Use your existing Rich Text Formula field with the iframe tag, but for the src, use the URL field that you just created. When you save this and put it on a form, it will still look like you're having the same problem, where the iframe tag displays as text rather than html.
Ex. "<iframe height=\"650px\" width=\"1200px\" src=\""&[URL]&"\"></iframe>"
3. Create a report link field. Under "Field relationship", under "Match the values in this
field from this table" choose the rich text formula field with the iframe tag. Then next to that, choose Select Target, find the app that you're in, then the table and rich text formula field again.
4. Add the report link to your form. Leave the behavior as the default "Display just a link." When you open the form, you should be able to see whatever your'e trying to embed.
